Network control system

ABSTRACT

First and second stations have first and second memory elements ( 2, 3 ) for storing first and second shared data, respectively, and a data transfer system (DT 1 ) includes third and fourth memory elements (CM  12,  CM  14 ) for storing third and fourth shared data, respectively, first and second transfer period determiner (CNT  90,  CNT  92 ), a first transfer element ( 26   a ) working to operate in accordance with the first transfer period to have the second shared data stored in the fourth memory element (CM  14 ) and operate in accordance with the second transfer period to have the first shared data stored in the third memory element (CM  12 ), a second transfer element ( 26   b ) working for transfer of shared data between the fourth memory element (CM  14 ) and the third memory element (CM  12 ), and a third transfer element ( 26   c ) working to operate in accordance with the second transfer period to have the fourth shared data stored in the second memory element ( 3 ) and operate in accordance with the first transfer period to have the third shared data stored in the first memory element ( 2 ).

TECHNICAL FIELD

The present invention relates to a network control system widely usedfor control of industrial systems, such as those in, among others, ironand steel making plants or paper making plants, FA fields includingassembly operations such as in automobile industries, PA fields such asfor chemical plants, or water supply and sewerage systems or otherpublic systems.

BACKGROUND ART

For control of plant equipments, there have been typical plant controlsystems including those configured with control devices interconnectedthrough a network to implement data transfer between control devices viathe network. Also, there have been plant control systems for large-scaleplants, including those configured with control devices increased innumber and accompanied by a set of superordinate networks hierarchicallyarchitected to implement data transfer between networks.

Still also, there has been use of a set of sub-network repeatersdescribed in a patent literature 1 (Japanese Patent ApplicationLaying-open Publication No. 5-336118), for instance, to constitute aplant control system.

FIG. 18 is a conceptual diagram showing a concept of data transfer in aplant control system in the past.

As shown in FIG. 18, the plant control system 100 in the past had datatransfer systems DT104, DT105, and DT106 interconnected through anetwork N110. The data transfer system DT104 was connected through asub-network N101 to n sub-network stations STN111 to STN11 n. Likewisethe data transfer system DT105 was connected through a sub-network N102to n sub-network stations STN121 to STN12 n, and the data transfersystem DT106 was connected through a sub-network N103 to n sub-networkstations STN131 to STN13 n.

The n sub-network stations STN111 to STN11 n were connected with ncontrol devices PCS111 to PCS11 n, respectively. Likewise the nsub-network stations STN121 to STN12 n were connected with n controldevices PCS121 to PCS12 n, respectively, and the n sub-network stationsSTN131 to STN13 n were connected with n control devices PCS131 to PCS13n, respectively.

There was combination of a memory shared to be common in sub-network 101for STN11Data to STN1 nData to be defined, a memory shared to be commonin sub-network 102 for STN21Data to STN2 nData to be defined, and amemory shared to be common in sub-network 103 for STN31Data to STN3nData to be defined.

In such the configuration, for transfer of data between a certainsub-network and any sub-network else, implemented was a transfer of datathrough network 110 using data transfer systems DT104, DT105, and/orDT106.

For instance, as illustrated in FIG. 18, for pieces of data STN11Dataand STN12Data in the memory shared in the sub-network N101 to be used ata control device PCS121 connected to the sub-network N 102, there was anoperation of the data transfer system DT104 to have the pieces of dataSTN11Data and STN12Data in the shared memory in the sub-network N101once transferred through the superordinate network N110 to the datatransfer system DT105. Then, the data transfer system DT105 wasoperated, so that the transferred data STN and STN12Data of sharedmemory were transferred to sub-network stations STN121 to STN12 n, aspieces of data to be shared under the sub-network N102.

SUMMARY OF INVENTION

However, the plant control system in the past had four problems, asfollows.

As a first problem, there was an increase in cost of fabrication as wellas in cost of maintenance due to complexity of system configuration.That is, for transfer of data between sub-networks, there was neededprovision of data transfer systems DT104, DT105, and DT106 and asuperordinate network N 110, with an increased cost in fabrication ofplant control system. Further, as a problem in an entirety of plantcontrol system, there was a failure rate increased as the system numberincreased, with increased expenses for the maintenance.

As a second problem, there was a decrease in transfer rate of data. Thatis, for any piece of data in shared memory in an individual sub-networkto be used in another network, it was necessitated to have the data ofshared memory in the sub-network once transferred via a route for datatransfer to a superordinate network N110, and make an additionaltransfer of data of shared memory through a data transfer system to asub-network connected to a control device needing the data of sharedmemory. As a result, the data transfer rate was reduced, as a problem.

In the example illustrated in FIG. 18, for use of data STN11Data andSTN12Data in shared memory in a sub-network N101 being wanted at acontrol device PCS21 connected to a sub-network N102, there wasoperation of a data transfer system DT104 to transfer the sub-networkN101′s shared memory data STN11Data and STN12Data once to a datatransfer system DT105, via a superordinate network N110, as described.This was followed by operation of the data transfer system DT105, asnecessary for the transferred shared memory data STN11Data and STN12Datato be transferred to sub-network stations STN121 to STN12 n, as data tobe shared in the sub-network N102. Hence, sometimes there appearedreduction of data transfer rate.

As a third problem, there was transfer of data not always optimum, suchas disabled transfer of latest data to sub-networks, or repeatedtransfer of identical data.

FIG. 19 is a time chart showing data transfer timings for transfer ofdata from a sub-network to another sub-network.

As illustrated in FIG. 19, there was a transfer period 101 a as a periodof transfer in the sub-network N101, there being a transfer period 102 aas a period of transfer in the sub-network N102, and a transfer period100 a as a period of transfer between sub-networks.

First, the data transfer system DT104 was operated at a transfer timingaccording to the transfer period 101 a, to transfer one of data 101 e to101 i to be transferred to sub-network stations STN111 to STN11 nconnected to the sub-network N101.

Then, at a time t1, the data transfer system DT104 received a transferdata 102 f transferred from the data transfer system DT105 through thesuperordinate network N110, in accordance with the transfer period 100a. Further, at a time t2, the data transfer system DT104 was operatedfor a transfer of transfer data 101 f according to the transfer period101 a, which was followed by its operation to transfer the receivedtransfer data 102 f to the sub-network stations STN111 to STN11 n.

Next, at a time t3, the data transfer system DT104 was operated for atransfer of transfer data 101 g according to the transfer period 101 a,which was followed by its operation to transfer the received transferdata 102 f again to the sub-network stations STN111 to STN11 n.

Such being the case, there was a difference between the transfer period100 a and the transfer period 101 a, causing the data transfer systemDT104 to transfer the transfer data 102 f twice to the sub-networkstations STN111 to STN11 n.

Next, at a time t4, the data transfer system DT104 received a transferdata 102 g transferred from the data transfer system DT105 through thesuperordinate network N110, in accordance with the transfer period 100a.

Then, at a time t5, the data transfer system DT104 was operated for atransfer of transfer data 101 h according to the transfer period 101 a,which was followed by its operation to transfer the received transferdata 102g to the sub-network stations STN111 to STN11 n.

Such being the case, due to the difference between the transfer period100 a and the transfer period 101 a, the data transfer system DT104 wassubject to a difference between a time interval (t1 to t2) fromreception to transfer of the transfer data 102 f and a time interval (t4to t5) from reception to transfer of the transfer data 102 g. It wasthus not always a latest transfer data from the data transfer systemDT105 that was transferred to the sub-network stations STN111 to STN11n.

Such being the case, sometimes there appeared un-optimized data amongtransferred data from the data transfer system DT105 to the sub-networkstations STN111 to STN11 n.

Likewise, sometimes there appeared un-optimized data among transferreddata from the data transfer system DT104 to sub-network stations STN121to STN12 n, too.

As a fourth problem, there was a complicate processing due to mismatchedaddresses in shared memories. That is, for identical data in the plantcontrol system in the past, there was a discrepancy between a sharedmemory address in the superordinate network N110 and a shared memoryaddress in a respective sub-network. Also, for identical data, therewere mismatched addresses in shared memories even between sub-networks.As a result, there were overly complicated engineering tasks, such asthose in data transfer setup in plant control system.

In the example illustrated in FIG. 18, there were data STN11Data andSTN12Data of shared memory in the sub-network N101 transferred throughthe data transfer system DT104 to the superordinate network N110, withaddresses of shared memory data STN11Data and STN12Data on thesub-network N101 being mismatched to addresses of shared memory dataSTN11Data and STN12Data on the superordinate network N110. The addressesof shared memory data STN11Data and STN12Data on the sub-network N101were mismatched to addresses of shared memory data STN11Data andSTN12Data on the sub-network N102, too. As a result, there werecomplicated engineering tasks, such as those in data transfer setup inplant control system, giving rise to significant task loads on workers.

The present invention has been devised in view of the problemsdescribed, and it is an object of the present invention to provide anetwork control system with a simplified system configuration leading toa reduced cost, allowing for an enhanced efficiency in network transfer,an optimized transfer data, and a facilitated engineering.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1( a) is an explanatory diagram showing internal configurations ofshared memories in a network control system according to a firstembodiment of the present invention, and FIG. 1( b) is a configurationdiagram showing a system configuration of the network control systemaccording to the first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a hardware configuration of adata transfer system DT1 in the network control system 1 according tothe first embodiment.

FIG. 3 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 according to thefirst embodiment of the present invention.

FIG. 4 is a time chart showing data transfer timings for transfer ofdata between a network N1 and a network N2.

FIG. 5( a) is an explanatory diagram showing internal configurations ofshared memories in a network control system according to a secondembodiment of the present invention, and FIG. 5( b) is a configurationdiagram showing a system configuration of the network control systemaccording to the second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a hardware configuration of adata transfer system DT5 in the network control system 1 b according tothe second embodiment.

FIG. 7 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3.

FIG. 8 is an explanatory diagram showing an example of global sharedmemory area 11 set up as an army of consecutive areas from a beginningaddress.

FIG. 9 is a configuration diagram showing a system configuration of anetwork control system 1 c according to a third embodiment.

FIG. 10 is an explanatory diagram showing an example of global sharedmemory area set up with memory areas according to shared settinginformation.

FIG. 11 is a configuration diagram showing a system configuration of anetwork control system 1 d according to a fourth embodiment.

FIG. 12 is a configuration diagram showing a hardware configuration of adata transfer system DT7 in the network control system 1 d according tothe fourth embodiment.

FIG. 13 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 d according tothe fourth embodiment of the present invention.

FIG. 14 is a configuration diagram showing a hardware configuration of adata transfer system DT8 in a network control system 1 e according to afifth embodiment.

FIG. 15 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 e according tothe fifth embodiment of the present invention.

FIG. 16 is a configuration diagram showing a system configuration of anetwork control system 1 f according to a sixth embodiment.

FIG. 17 is a configuration diagram showing a system configuration of anetwork control system 1 g according to a seventh embodiment.

FIG. 18 is a conceptual diagram showing a concept of data transfer in aplant control system in the past

FIG. 19 is a time chart showing data transfer timings for transfer ofdata from a sub-network to another sub-network.

DESCRIPTION OF EMBODIMENTS

There will be description of embodiments with reference to drawings.

First Embodiment

FIG. 1( a) is an explanatory diagram showing internal configurations ofshared memories in a network control system according to a firstembodiment of the present invention, and FIG. 1( b) is a configurationdiagram showing a system configuration of the network control systemaccording to the first embodiment of the present invention.

As shown in FIG. 1( b), the network control system 1 according to thefirst embodiment includes a data transfer system DT1, a data transfersystem DT2, a set of n stations STN11 to STN1 n, a set of n stationsSTN21 to STN2 n, and a set of n stations STN31 to STN3 n. The datatransfer system DT1 and stations STN11 to STN are interconnected througha network N1. Between the data transfer system DT1 and stations STN21 toSTN2 n, as well as between the data transfer system DT2 and the stationsSTN21 to STN2 n, there are interconnections through a network N2. Thedata transfer system DT2 and stations STN31 to STN3 n are interconnectedthrough a network N3.

Further, the network control system 1 includes a set of n controldevices PCS11 to PCS1 n connected with stations under the network N1,respectively, a set of n control devices PCS21 to PCS2 n connected withstations under the network N2, respectively, and a set of n controldevices PCS31 to PCS3 n connected with stations under the network N3,respectively.

As shown in FIG. 1( a), the network N1 has a shared memory 2 configuredas illustrated, the stations STN11 to STN1 n as well as the datatransfer system DT1 being each provided with a shared memory similarthereto in configuration. The network N2 has a shared memory 3configured as illustrated, the stations STN21 to STN2 n as well as thedata transfer system DT1 and the data transfer system DT2 being eachprovided with a shared memory similar thereto in configuration. Thenetwork N3 has a shared memory 4 configured as illustrated, the stationsSTN31 to STN3 n as well as the data transfer system DT2 being eachprovided with a shared memory similar thereto in configuration.

The shared memory 2 of network N1, the shared memory 3 of network N2,and the shared memory 4 of network N3 have areas thereof each dividedinto an area set up as (a global shared memory area 2 a, 3 a, or 4 a)being sharable to be common among the networks N1, N2, and N3, and anarea set up as (a local shared memory area 2 b, 3 b, or 4 b) beingeffective simply within the network N1, N2, or N3, respectively. Theglobal shared memory areas have sets of data stored therein each havingan identical address over the shared memories of networks N1, N2, andN3.

FIG. 2 is a configuration diagram showing a hardware configuration ofthe data transfer system DT1 in the network control system 1 accordingto the first embodiment. It is noted that the data transfer system DT2is similar in configuration to the data transfer system DT1, anddescription thereof is omitted.

As shown in FIG. 2, in the network control system 1 according to thefirst embodiment, the data transfer system DT1 includes a combination ofT/R's 21 and 29 configured as transmitter receiver sets, a combinationof MAC's 22 and 30 configured as medium access controllers, acombination of ARB's 23 and 31 configured as bus traffic arbitrators, aCM 12 configured as a common memory shared in the network N1, a CM 14configured as a common memory shared in the network N2, a DMA 25, an MPU26 configured for central control, an I/F 27 configured as a transferparameter in-taking interface, an FROM 28 configured as a transferparameter memory, a combination of CNT's 90 and 92 configured astransfer controllers, and a combination of WAT's 91 and 93 configured astransfer period monitors.

The CM 12 is divided, like the shared memory 2 illustrated in FIG. 1(a), into an area set up as (a global shared memory area 12 a) beingshamble to be common among the networks N1 to N3, and an area set up as(a local shared memory area 12 b) being effective simply within thenetwork N1.

Also the CM 14 is divided, like the shared memory 3 illustrated in FIG.1( a), into an area set up as (a global shared memory area 14 a) beingshamble to be common among the networks N1 to N3, and an area set up as(a local shared memory area 14 b) being effective simply within thenetwork N2.

The CNT 90 is configured to determine a first transfer period as atransfer period in transfer of shared data from the data transfer systemDT1 to stations STN11 to STN1 n.

The WAT 91 is configured to work in accordance with the first transferperiod determined by the CNT 90, to detect a time point of transfer ofshared data from the data transfer system DT1 to stations STN11 to STN1n, as a second transfer timing. Further, the WAT 91 is configured todetect a time point of reception of shared data from any of stationsSTN21 to STN2 n to the data transfer system DT1, as a first transfertiming to be a time point earlier than the second transfer timing by aprescribed time interval. And, the WAT 91 is adapted to work upondetection of the first transfer timing or the second transfer timing, tosupply the MPU 26 with a signal representing the detection.

The CNT 92 is configured to determine a second transfer period as atransfer period in transfer of shared data from the data transfer systemDT1 to stations STN21 to STN2 n.

The WAT 93 is configured to work in accordance with the second transferperiod determined by the CNT 92, to detect a time point of transfer ofshared data from the data transfer system DT1 to stations STN21 to STN2n, as a fourth transfer timing. Further, the WAT 93 is configured todetect a time point of reception of shared data from any of stationsSTN11 to STN1 n to the data transfer system DT1, as a third transfertiming to be a time point earlier than the fourth transfer timing by aprescribed time interval. And, the WAT 93 is adapted to work upondetection of the third transfer timing or the fourth transfer timing, tosupply the MPU 26 with a signal representing the detection.

Further, the FROM 28 has stored therein pieces of information on sharedmemories as targets of global shared memories on the networks. Morespecifically, the FROM 28 has stored therein sets of addresses of globalmemory areas and directions data transfer associated therewith, asinformation on shared memories.

Such pieces of information on shared memories are stored in the FROM 28from an external interface, through the I/F 27 configured as a transferparameter in-taking interface, and the MPU 26. Also, there may be piecesof information on shared memories taken in as targets of global sharedmemories, through the network N1 or the network N2.

Functionally, the MPU 26 is configured with a first transfer means 26 a,a second transfer means 26 b, and a third transfer means 26 c. And, thefirst transfer means 26 a, the second transfer means 26 b, and the thirdtransfer means 26 c are each adapted to read pieces of information onglobal shared memories in the FROM 28, to make the following controlactions in accordance with read information on setting.

At the MPU 26, the first transfer means 26 a is adapted to operate inaccordance with a first transfer period determined by the CNT 90, tohave pieces of shared data as stored in global shared memory areas ofstations STN21 to STN2 n, stored in a global shared memory area of theCM 14, with addresses identical to their addresses in those globalshared memory areas.

More specifically, the first transfer means 26 a operates, at a firsttransfer timing, to store in the CM 14 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31.

Further, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a second transfer period determined by theCNT 92, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN1 n, stored in a global shared memory areaof the CM 12, with addresses identical to their addresses in thoseglobal shared memory areas.

More specifically, the first transfer means 26 a operates, at a thirdtransfer timing, to store in the CM 12 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23.

At the MPU 26, the second transfer means 26 b is adapted to operate, asthe CM 12 has pieces of shared data stored in the global shared memoryarea by the first transfer means 26 a, to store the pieces of shareddata in the global shared memory area of the CM 14, with addressesidentical to their addresses in the global shared memory area of the CM12.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 12, stored in the global shared memory area of the CM 14, byemploying the ARB 23, the DMA 25, and the ARB 31.

Further, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 14 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory area of the CM 12, withaddresses identical to their addresses in the global shared memory areaof the CM 14.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 14, stored in the global shared memory area of the CM 12, byemploying the ARB 31, the DMA 25, and the ARB 23.

At the MPU 26, the third transfer means 26 c is adapted to operate inaccordance with a second transfer period supplied from the WAT 93, tohave pieces of shared data as stored in the global shared memory area ofthe CM 14, stored in global shared memory areas of stations STN21 toSTN2 n, with addresses identical to their addresses in the global sharedmemory area of the CM 14.

More specifically, the third transfer means 26 c operates, at a fourthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 14, stored in the global shared memoryareas of stations STN21 to STN2 n, by employing the ARB 31, the MAC 30,and the UR 29.

Further, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a first transfer period supplied from the WAT91, to have pieces of shared data as stored in the global shared memoryarea of the CM 12, stored in global shared memory areas of stationsSTN11 to STN1 n, with addresses identical to their addresses in theglobal shared memory area of the CM 12.

More specifically, the third transfer means 26 c operates, at a secondtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 12, stored in the global shared memoryareas of stations STN11 to STN1 n, by employing the ARB 23, the MAC 22,and the T/R 21.

Description is now made of actions of the network control system 1according to the first embodiment of the present invention, withreference to FIG. 3.

FIG. 3 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 according to thefirst embodiment of the present invention.

In FIG. 3, there is a set of stations STN11 to STN1 n connected to thenetwork N1, of which a single station STN11 is depicted for simplifieddescription. Likewise, there is a set of stations STN21 to STN2 nconnected to the network N2, of which a single station STN21 isdepicted, there being a set of stations STN31 to STN3 n connected to thenetwork N3, of which a single station STN31 is depicted.

As illustrated in FIG. 3, there is a combination of n stations STN11 toSTN1 n, data transfer system DT1, n stations STN21 to STN2 n, datatransfer system DT2, and n stations STN31 to STN3 n each respectivelyincluding a memory or memories (2, 12, 14, 3, 15, 17, 4) shared to becommon. Each shared memory is divided into, to set up, a global sharedmemory area (2 a, 12 a, 14 a, 3 a, 15 a, 17 a, or 4 a) sharable to becommon among the networks N1, N2, and N3, and a local shared memory area(2 b, 12 b, 14 b, 3 b, 15 b, 17 b, or 4 b) effective simply within acorresponding one of the networks.

There comes transfer of shared data to stations STN11 to STN1 n with atransfer period referred herein to as a first transfer period, therecoming transfer of shared data to stations STN21 to STN2 n with atransfer period referred herein to as a second transfer period, andtransfer of shared data to stations STN31 to STN3 n with a transferperiod referred herein to as a third transfer period.

And, the data transfer system DT1 is adapted to work in accordance withthe first transfer period, to detect a first transfer timing as a timepoint of transfer of shared data from stations STN21 to STN2 n to thedata transfer system DT1, and a second transfer timing as a time pointof transfer of shared data from the data transfer system DT1 to stationsSTN11 to STN1 n.

The data transfer system DT1 is adapted to work in accordance with thesecond transfer period, to detect a third transfer timing as a timepoint of transfer of shared data from stations STN11 to STN1 n to thedata transfer system DT1, and a fourth transfer timing as a time pointof transfer of shared data from the data transfer system DT1 to stationsSTN21 to STN2 n.

The data transfer system DT2 is adapted to work in accordance with thethird transfer period, to detect a fifth transfer timing as a time pointof transfer of shared data from stations STN21 to STN2 n to the datatransfer system D12, and a sixth transfer timing as a time point oftransfer of shared data from the data transfer system DT2 to stationsSTN31 to STN3 n.

The data transfer system DT2 is adapted to work in accordance with thesecond transfer period, to detect a seventh transfer timing as a timepoint of transfer of shared data from stations STN31 to STN3 n to thedata transfer system DT2, and an eighth transfer timing as a time pointof transfer of shared data from the data transfer system DT2 to stationsSTN21 to STN2 n.

Description is now first made of actions of the network control system 1along with operation of a control device PCS11 connected with a stationSTN11 in the network N1 to update a piece of shared data stored inglobal shared memory areas 2 a.

As shown in FIG. 3, in the network N1, the station STN11 has a shareddata “STN11Data” written at an address 5 in a shared memory area (as aglobal shared memory area 2 a) thereof by a control device PCS11connected with the station STN11, whereby the station STN11 works totransfer the written shared data “STN11Data” to a whole of stationsSTN12 to STN1 n in the network N1 with the data transfer system DT1inclusive.

And, the data transfer system DT1 detects a third transfer timing,whereby it works to receive the transferred shared data “STN11Data”, andstore the received shared data “STN11Data” at an address 5 in a sharedmemory area (as a global shared memory area 12 a) thereof.

Next, the data transfer system DT1 works to have the shared data“STN11Data”, as it is stored at the address 5 in the shared memory area(as the global shared memory area 12 a), stored at an address 5 in ashared memory area (as a global shared memory area 14 a) thereof.

The data transfer system DT1 detects a fourth transfer timing, wherebyit works to transfer the shared data “STN11Data” as stored at theaddress 5 in the shared memory area (as the global shared memory area 14a) to whole stations STN21 to STN2 n (FIG. 3 simply depicts the stationSTN21) connected to the network N2. And, the stations STN21 to STN2 neach respectively have the transferred shared data “STN11Data” stored atan address 5 in a shared memory area (as a global shared memory area 3a) thereof.

Next, the station STN21 transfers the stored data “STN11Data” to a wholeof stations STN22 to STN2 n in the network N2 with the data transfersystem DT2 inclusive.

And, the data transfer system DT2 detects a fifth transfer timing,whereby it works to receive the transferred shared data “STN11Data”, andstore the received shared data “STN11Data” at an address 5 in a sharedmemory area (as a global shared memory area 15 a) thereof.

Next, the data transfer system DT2 works to have the shared data“STN11Data”, as it is stored at the address 5 in the shared memory area(as the global shared memory area 15 a), stored at an address 5 in ashared memory area (as a global shared memory area 17 a) thereof.

The data transfer system DT2 detects a sixth transfer timing, whereby itworks to transfer the shared data “STN11Data” as stored at the address 5in the shared memory area (as the global shared memory area 17 a) towhole stations STN31 to STN3 n (FIG. 3 simply depicts the station STN31)connected to the network N3. And, the stations STN31 to STN3 n eachrespectively have the transferred shared data “STN11Data” stored at anaddress 5 in a shared memory area (as a global shared memory area 4 a)thereof.

It therefore is possible for a control device PCS31 to read the data“STN11Data” transferred to the station STN31 in the network N3.

Description is now made of actions of the network control system 1 alongwith operation of the control device PCS31 connected with the stationSTN31 in the network N3 to update a piece of shared data stored inglobal shared memory areas 4 a.

As shown in FIG. 3, in the network N3, the control device PCS31connected with the station STN31 writes a data “STN31Data” at an address7 in the shared memory area (as the global shared memory area 4 a) ofthe station STN31, whereby the station STN31 works to transfer thewritten data “STN31Data” to a whole of stations STN32 to STN3 n in thenetwork N3 with the data transfer system DT2 inclusive.

And, the data transfer system DT2 detects a seventh transfer timing,whereby it works to receive the transferred shared data “STN31Data”, andstore the received shared data “STN31Data” at an address 7 in the sharedmemory area (as the global shared memory area 17 a).

Next, the data transfer system DT2 works to have the shared data“STN31Data”, as it is stored at the address 7 in the shared memory area(as the global shared memory area 17 a), stored at an address 7 in theshared memory area (as the global shared memory area 15 a).

The data transfer system DT2 detects an eights transfer timing, wherebyit works to transfer the shared data “STN31Data” as stored at theaddress 7 in the shared memory area (as the global shared memory area 15a) to whole stations STN21 to STN2 n connected to the network N2. And,the stations STN21 to STN2 n each respectively have the transferredshared data “STN31Data” stored at an address 7 in a shared memory area(as a global shared memory area 3 a) thereof.

Next, the station STN21 transfers the stored data “STN31Data” to a wholeof stations STN22 to STN2 n in the network N2 with the data transfersystem DT2 inclusive.

And, the data transfer system DT1 detects a first transfer timing,whereby it works to receive the transferred shared data “STN31Data”, andstore the received shared data “STN31Data” at an address 5 in the sharedmemory area (as the global shared memory area 14 a).

Next, the data transfer system DT1 works to have the shared data“STN31Data”, as it is stored at the address 7 in the shared memory area(as the global shared memory area 14 a), stored at an address 7 in theshared memory area (as the global shared memory area 12 a).

The data transfer system DT1 detects a second transfer timing, wherebyit works to transfer the shared data “STN31Data” as stored at theaddress 7 in the shared memory area (as the global shared memory area 12a) to whole stations STN11 to STN1 n connected to the network N1. And,the stations STN11 to STN1 n each respectively have the transferredshared data “STN31Data” stored at an address 7 in the shared memory area(as the global shared memory area 2 a).

It therefore is possible for the control device PCS11 to read the data“STN31Data” transferred to the station STN11 in the network N1.

It is noted that in the example illustrated in FIG. 3 the data transfersystem DT1 as well as DT2 has a combination of stations directlyconnected thereto as a first station and a second station. That is, tothe data transfer system DT1, connected is a combination of stationSTN11 as a first station, and station STN21 as a second station. Alsofor the data transfer system DT2, connected thereto is a combination ofstation STN21 as a first station, and station STN31 as a second station

For the data transfer system DT1, letting the station STN11 be a firststation connected thereto, and the station STN21 be a second station,the station STN11 has a shared memory area (as a global shared memoryarea 2 a) corresponding to a first memory element, the station STN21having a shared memory area (as a global shared memory area 3 a)corresponding to a second memory element, the data transfer system DT1having a shared memory area (as a global shared memory area 12 a)corresponding to a third memory element, the data transfer system DT1having a shared memory area (as a global shared memory area 14 a)corresponding to a fourth memory element.

FIG. 4 is a time chart of timings for data transfer in transfer of databetween the network N1 and the network N2.

As illustrated in FIG. 4, there is a first transfer period 201 as aperiod of transfer in the network N1, that is, a transfer period intransfer of shared data from the data transfer system DT1 to stationsSTN11 to STN1 n. Also, there is a second transfer period 202 as a periodof transfer in the network N2, that is, a transfer period in transfer ofshared data from the data transfer system DT1 to stations STN21 to STN2n.

First, at a time point t1, the data transfer system DT1 detects a firsttransfer timing, when it works to receive a shared data 202 atransferred from any of stations STN21 to STN2 n.

Then, at a time point t2, the data transfer system DT1 detects a secondtransfer timing, when it works to transfer the shared data 202 a tostations STN11 to STN1 n.

Also afterward, the data transfer system DT1 likewise works at each offirst timing and second timing, to receive or transfer shared data.

Further, at a time point t3, the data transfer system DT1 detects athird transfer timing, when it works to receive a shared data 201 btransferred from any of stations STN11 to STN1 n.

Then, at a time point t4, the data transfer system DT1 detects a fourthtransfer timing, when it works to transfer the shared data 201 b tostations STN21 to STN2 n.

Also afterward, the data transfer system DT1 likewise works at each ofthird timing and fourth timing, to receive or transfer shared data.

Such being the case, the data transfer system DT1 is adapted to work fordata transfer in accordance with a transfer period of a network at adestination of transfer, affording to eliminate repetition of transferof a shared data, thus always allowing for transfer of fresh shareddata.

As is apparent from the foregoing, in the network control system 1according to the first embodiment of the present invention, respectivenetworks N1, N2, and N3 have their shared memory spaces divided intoglobal shared memory areas shared to be common among the networks, andlocal shared memory areas independently set up for each of the networksN1, N2, and N3, thus eliminating the need of a superordinate network 110in the past. There is no costing hardware for superordinate network 110,nor costing setup engineering for architecture of shared memory, thusaffording to reduce an entire cost of network control system for plantcontrol.

Further, there is a whole set of data stored in global shared memoryareas 11 as data to be transferred between networks, permitting highrate transfer of data among whole networks N1, N2, and N3, withoutprovision of superordinate network 110.

Further, there is transfer of data performed in accordance with atransfer period of a network at a destination end, allowing for anoptimal transfer of shared data.

Further, at each of the networks N1, N2, and N3, there is a set of datastored in local shared memory areas independently set for the network,simply permitting an intra-network transfer at the network N1, N2, orN3, allowing for an enhanced efficiency in communication of entirenetwork.

Further, there is a set of data stored in global shared memory areasshared to be common among the networks N1, N2, and N3, with commonaddresses among the networks, allowing for a facilitated engineering andtrouble-shooting by user.

Second Embodiment

FIG. 5( a) is an explanatory diagram showing internal configurations ofshared memories in a network control system according to a secondembodiment of the present invention, and FIG. 5( b) is a configurationdiagram showing a system configuration of the network control systemaccording to the first embodiment of the present invention.

As shown in FIG. 5( b), the network control system 1 b according to thesecond embodiment includes a data transfer system DT5 and a datatransfer system DT6, substituting for the data transfer systems DT1 andDT2 as constituent parts of the network control system 1 according tothe first embodiment, respectively.

Further, there are networks N1 to N3 including stations having theirshared memories each divided into sub-areas, by orders of priority ofshared data, as illustrated in FIG. 5( a). More specifically, in thenetwork N1, each shared memory 50 a is divided into classes of transferrate as set up in three ranks being a high transfer rate block 36, amedium transfer rate block 37, and a low transfer rate block 38. Also inthe network N2, each shared memory 54 a is divided into prioritizedclasses likewise set up in three ranks, as well as each shared memory 58a in the network N3.

FIG. 6 is a configuration diagram showing a hardware configuration ofthe data transfer system DT5 in the network control system 1 b accordingto the second embodiment. It is noted that the data transfer system DT6is similar in configuration to the data transfer system DT5, anddescription thereof is omitted.

As shown in FIG. 6, in the network control system 1 b according to thesecond embodiment, the data transfer system DT5 includes a combinationof T/R's 21 and 29 configured as transmitter receiver sets, acombination of MAC's 22 and 30 configured as medium access controllers,a combination of ARB's 23 and 31 configured as bus traffic arbitrators,a CM 51 configured as a common memory shared in the network N1, a CM 53configured as a common memory shared in the network N2, a DMA 25, an MPU26 configured for central control, an I/F 27 configured as a transferparameter in-taking interface, an FROM 28 configured as a transferparameter memory, a PRI 49 configured as a transfer priority degreemanager, a combination of CNT's 90 and 92 configured as transfercontrollers, and a combination of WAT's 91 and 93 configured as transferperiod monitors.

The CM 51 is divided, like a shared memory 50 illustrated in FIG. 5( a),into an area set up as (a global shared memory area 51 a) being sharableto be common among the networks N1 to N3, and an area set up as (a localshared memory area 51 b) being effective simply within the network N1.Further, the global shared memory area 51 a is divided into sub-areas,by orders of priority of shared data, like the shared memory 50illustrated in FIG. 5( a). More specifically, the global shared memoryarea 51 a is divided into classes of transfer rate as set up in threeranks being a high transfer rate block 36, a medium transfer rate block37, and a low transfer rate block 38.

The CM 53 is divided, like a shared memory 54 illustrated in FIG. 5( a),into an area set up as (a global shared memory area 53 a) being sharableto be common among the networks N1 to N3, and an area set up as (a localshared memory area 53 b) being effective simply within the network N2.Further, the global shared memory area 53 a is divided into sub-areas,by orders of priority of shared data, like the shared memory 54illustrated in FIG. 5( a). More specifically, the global shared memoryarea 53 a is divided into classes of transfer rate as set up in threeranks being a high transfer rate block 36, a medium transfer rate block37, and a low transfer rate block 38.

The PRI 49 is configured to store therein, as pieces of information onorder of priority, respective orders of priorities in transfer of shareddata between the data transfer system DT5 and a set of stations STN11 toSTN1 n, as well as between the data transfer system DT5 and a set ofstations STN21 to STN2 n. The priority order information stored includessets of addresses of global shared memory areas and associated orders ofpriorities each representing a high rate, a medium rate, or a low rate.

The CNT 90 is configured to read a piece of information on order ofpriority from the PRI 149, and work on the basis of information onpriority order, to determine a first transfer period as a transferperiod in transfer of shared data from the data transfer system DT5 tostations STN11 to STN1 n. More specifically, the CNT 90 selects atransfer period according to the priority order information representinga high rate, a medium rate, or a low rate, to provide the selectedtransfer period as a first transfer period. For instance, for a piece ofpriority order information representing a high rate, the CNT 90 selectsa high-rate transfer period, to provide as a first transfer period. TheMPU 26 is thereby adapted for transfer of a shared data in accordancewith the high-rate transfer period selected as a first transfer period.Making a transfer of shared data in accordance with a high-rate transferperiod selected as a transfer period will be referred herein to as ahigh rate transfer. Likewise, making a transfer of shared data inaccordance with a low-rate transfer period selected as a transfer periodwill be referred herein to as a low rate transfer.

The WAT 91 is configured to work in accordance with the first transferperiod determined by the CNT 90, to detect a time point of transfer ofshared data from the data transfer system DT5 to stations STN11 to STN1n, as a second transfer timing. Further, the WAT 91 is configured todetect a time point of reception of shared data from any of stationsSTN21 to STN2 n to the data transfer system DT5, as a first transfertiming to be a time point earlier than the second transfer timing by aprescribed time interval. And, the WAT 91 is adapted to work upondetection of the first transfer timing or the second transfer timing, tosupply the MPU 26 with a signal representing the detection.

The CNT 92 is configured to read a piece of information on order ofpriority from the PRI 149, and work on the basis of information onpriority order, to determine a second transfer period as a transferperiod in transfer of shared data from the data transfer system DT5 tostations STN21 to STN2 n. More specifically, the CNT 92 selects atransfer period according to the priority order information representinga high rate, a medium rate, or a low rate, to provide the selectedtransfer period as a second transfer period.

The WAT 93 is configured to work in accordance with the second transferperiod determined by the CNT 92, to detect a time point of transfer ofshared data from the data transfer system DT5 to stations STN21 to STN2n, as a fourth transfer timing. Further, the WAT 93 is configured todetect a time point of reception of shared data from any of stationsSTN11 to STN1 n to the data transfer system DT5, as a third transfertiming to be a time point earlier than the fourth transfer timing by aprescribed time interval. And, the WAT 93 is adapted to work upondetection of the third transfer timing or the fourth transfer timing, tosupply the MPU 26 with a signal representing the detection.

Functionally, the MPU 26 is configured with a first transfer means 26 a,a second transfer means 26 b, and a third transfer means 26 c. And, thefirst transfer means 26 a, the second transfer means 26 b, and the thirdtransfer means 26 c are each adapted to read pieces of information onglobal shared memories in the FROM 28, to make the following controlactions in accordance with read information on setting.

At the MPU 26, the first transfer means 26 a is adapted to operate inaccordance with a first transfer period determined by the CNT 90, tohave pieces of shared data as stored in global shared memory areas ofstations STN21 to STN2 n, stored in a global shared memory area of theCM 53, with addresses identical to their addresses in those globalshared memory areas.

More specifically, the first transfer means 26 a operates, at a firsttransfer timing, to store in the CM 53 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31.

Further, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a second transfer period determined by theCNT 92, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN1 n, stored in a global shared memory areaof the CM 51, with addresses identical to their addresses in thoseglobal shared memory areas.

More specifically, the first transfer means 26 a operates, at a thirdtransfer timing, to store in the CM 12 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23.

At the MPU 26, the second transfer means 26 b is adapted to operate, asthe CM 51 has pieces of shared data stored in the global shared memoryarea by the first transfer means 26 a, to store the pieces of shareddata in the global shared memory area of the CM 53, with addressesidentical to their addresses in the global shared memory area of the CM51.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 51, stored in the global shared memory area of the CM 53, byemploying the ARB 23, the DMA 25, and the ARB 31.

Further, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 14 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory area of the CM 12, withaddresses identical to their addresses in the global shared memory areaof the CM 14.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 53, stored in the global shared memory area of the CM 51, byemploying the ARB 31, the DMA 25, and the ARB 23.

At the MPU 26, the third transfer means 26 c is adapted to operate inaccordance with a second transfer period supplied from the WAT 93, tohave pieces of shared data as stored in the global shared memory area ofthe CM 53, stored in global shared memory areas of stations STN21 toSTN2 n, with addresses identical to their addresses in the global sharedmemory area of the CM 13.

More specifically, the third transfer means 26 c operates, at a fourthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 53, stored in the global shared memoryareas of stations STN21 to STN2 n, by employing the ARB 31, the MAC 30,and the T/R 29.

Further, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a first transfer period supplied from the WAT91, to have pieces of shared data as stored in the global shared memoryarea of the CM 51, stored in global shared memory areas of stationsSTN11 to STN1 n, with addresses identical to their addresses in theglobal shared memory area of the CM 51.

More specifically, the third transfer means 26 c operates, at a secondtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 51, stored in the global shared memoryareas of stations STN11 to STN1 n, by employing the ARB 23, the MAC 22,and the T/R 21.

Description is now made of actions of the network control system 1 baccording to the second embodiment of the present invention, withreference to FIG. 7.

FIG. 7 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 b according tothe second embodiment of the present invention.

In FIG. 7, there is a set of stations STN11 to STN1 n connected to thenetwork N1, of which a single station STN11 is depicted for simplifieddescription. Likewise, there is a set of stations STN21 to STN2 nconnected to the network N2, of which a single station STN21 isdepicted, there being a set of stations STN31 to STN3 n connected to thenetwork N3, of which a single station STN31 is depicted.

As illustrated in FIG. 7, there is a combination of n stations STN11 toSTN1 n, data transfer system DT5, n stations STN21 to STN2 n, datatransfer system DT6, and n stations STN31 to STN3 n each respectivelyincluding a memory or memories (50, 51, 53, 54, 55, 57, 58) shared to becommon. Each shared memory is divided into, to set up, a global sharedmemory area (50 a, 51 a, 53 a, 54 a, 55 a, 57 a, or 58 a) sharable to becommon among the networks N1, N2, and N3, and a local shared memory area(50 b, 51 b, 53 b, 54 b, 55 b, 57 b, or 58 b) effective simply within acorresponding one of the networks.

Further, the global shared memory area (50 a, 51 a, 53 a, 54 a, 55 a, 57a, or 58 a) is divided into classes of transfer rate as set up in ranksto be a high transfer rate block 36, a medium transfer rate block 37,and a low transfer rate block of 38.

There comes transfer of shared data to stations STN11 to STN1 n with atransfer period referred herein to as a first transfer period, therecoming transfer of shared data to stations STN21 to STN2 n with atransfer period referred herein to as a second transfer period, andtransfer of shared data to stations STN31 to STN3 n with a transferperiod referred herein to as a third transfer period. The first transferperiod is determined in correspondence to a piece of information onpriority order representing a high rate, a medium rate, or a low rate.Likewise, the second transfer period and the third transfer period alsoare each determined in correspondence to a piece of information onpriority order representing a high rate, a medium rate, or a low rate.

And, the data transfer system DT5 is adapted to work in accordance withthe first transfer period, to detect a first transfer timing as a timepoint of transfer of shared data from stations STN21 to STN2 n to thedata transfer system DT5, and a second transfer timing as a time pointof transfer of shared data from the data transfer system DT5 to stationsSTN11 to STN1 n.

The data transfer system DT5 is adapted to work in accordance with thesecond transfer period, to detect a third transfer timing as a timepoint of transfer of shared data from stations STN11 to STN1 n to thedata transfer system DT5, and a fourth transfer timing as a time pointof transfer of shared data from the data transfer system DT5 to stationsSTN21 to STN2 n.

The data transfer system DT6 is adapted to work in accordance with thethird transfer period, to detect a fifth transfer timing as a time pointof transfer of shared data from stations STN21 to STN2 n to the datatransfer system DT6, and a sixth transfer timing as a time point oftransfer of shared data from the data transfer system DT6 to stationsSTN31 to STN3 n.

The data transfer system DT6 is adapted to work in accordance with thesecond transfer period, to detect a seventh transfer timing as a timepoint of transfer of shared data from stations STN31 to STN3 n to thedata transfer system DT6, and an eighth transfer timing as a time pointof transfer of shared data from the data transfer system DT6 to stationsSTN21 to STN2 n.

Description is now first made of actions along with operation for acontrol device PCS11 connected with a station STN11 in the network N1 toupdate a piece of shared data stored in a high transfer rate block of aglobal shared memory areas 50 a.

As shown in FIG. 7, in the network N1, the control device PCS11connected with the station STN11 writes a data “STN11DataH” at anaddress 60 set in a high transfer rate block 36 of a shared memory area(as a global shared memory area 50 a) of the station STN11, whereby thestation STN11 works to high-rate transfer the written data “STN11DataH”to a whole of stations STN12 to STN1 n in the network N1 with the datatransfer system DT5 inclusive.

And, the data transfer system DT5 detects a third transfer timing,whereby it works to receive the transferred shared data “STN11DataH”,and store the received shared data “STN11DataH” at an address 60 set ina high transfer rate block 36 of a shared memory area (as a globalshared memory area 51 a) thereof.

Next, the data transfer system DT5 works to have the shared data“STN11DataH”, as it is stored at the address 60 in the shared memoryarea (as the global shared memory area 51 a), stored at an address 60set in a high transfer rate block 36 of a shared memory area (as aglobal shared memory area 53 a) thereof.

The data transfer system DT5 detects a fourth transfer timing, wherebyit works to high-rate transfer the shared data “STN11DataH” as stored atthe address 60 in the shared memory area (as the global shared memoryarea 53 a) to whole stations STN21 to STN2 n (FIG. 7 simply depicts thestation STN21) connected to the network N2. And, the stations STN21 toSTN2 n each respectively have the high-rate transferred shared data“STN11DataH” stored at an address 60 set in a high transfer rate block36 of a shared memory area (as a global shared memory area 54 a)thereof.

Next, the station STN21 high-rate transfers the stored data “STN11DataH”to a whole of stations STN22 to STN2 n in the network N2 with the datatransfer system DT6 inclusive.

And, the data transfer system DT6 detects a fifth transfer timing,whereby it works to receive the high-rate transferred shared data“STN11DataH”, and store the received shared data “STN11DataH” at anaddress 60 set in a high transfer rate block 36 of a shared memory area(as a global shared memory area 55 a) thereof.

Next, the data transfer system DT6 works to have the shared data“STN11DataH”, as it is stored at the address 60 in the shared memoryarea (as the global shared memory area 55 a), stored at an address 60set in a high transfer rate block 36 of a shared memory area (as aglobal shared memory area 57 a) thereof.

The data transfer system DT6 detects a sixth transfer timing, whereby itworks to high-rate transfer the shared data “STN11DataH” as stored atthe address 60 in the shared memory area (as the global shared memoryarea 57 a) to whole stations STN31 to STN3 n (FIG. 7 simply depicts thestation STN31) connected to the network N3. And, the stations STN31 toSTN3 n each respectively have the high-rate transferred shared data“STN11DataH” stored at an address 60 set in a high transfer rate block36 of a shared memory area (as a global shared memory area 58 a)thereof.

It therefore is possible for a control device PCS31 to read the data“STN11DataH” transferred to the station STN31 in the network N3.

Description is now made of actions along with operation for the controldevice PCS31 connected with the station STN31 in the network N3 toupdate a piece of shared data stored in a low transfer rate block of theglobal shared memory areas 58 a.

As shown in FIG. 7, in the network N3, the control device PCS31connected with the station STN31 writes a data “STN31DataL” at anaddress 62 set in a low transfer rate block 38 of the shared memory area(as the global shared memory area 58 a) of the station STN31, wherebythe station STN31 works to low-rate transfer the written data“STN31DataL” to a whole of stations STN32 to STN3 n in the network N3with the data transfer system DT6 inclusive.

And, the data transfer system DT6 detects a seventh transfer timing,whereby it works to receive the low-rate transferred shared data“STN31DataL”, and store the received shared data “STN31DataL” at anaddress 62 set in a low transfer rate block 38 of the shared memory area(as the global shared memory area 57 a).

Next, the data transfer system DT6 works to have the shared data“STN31DataL”, as it is stored at the address 62 in the shared memoryarea (as the global shared memory area 57 a), stored at an address 62set in a low transfer rate block 38 of the shared memory area (as theglobal shared memory area 55 a).

The data transfer system DT6 detects an eighth transfer timing, wherebyit works to low-rate transfer the shared data “STN31DataL” as stored atthe address 62 in the shared memory area (as the global shared memoryarea 55 a) to whole stations STN21 to STN2 n connected to the networkN2. And, the stations STN21 to STN2 n each respectively have thetransferred shared data “STN31DataL” stored at an address 62 set in alow transfer rate block 38 of the shared memory area (as the globalshared memory area 54 a).

Next, the station STN21 low-rate transfers the stored data “STN31DataL”to a whole of stations STN22 to STN2 n in the network N2 with the datatransfer system DT5 inclusive.

And, the data transfer system DT5 detects a first transfer timing,whereby it works to receive the transferred shared data “STN31DataL”,and store the received shared data “STN31DataL” at an address 62 set ina low transfer rate block 38 of the shared memory area (as the globalshared memory area 53 a).

Next, the data transfer system DT5 works to have the shared data“STN31DataL”, as it is stored at the address 62 in the shared memoryarea (as the global shared memory area 53 a), stored at an address 62set in a low transfer rate block 38 of the shared memory area (as theglobal shared memory area 51 a).

The data transfer system DT5 detects a second transfer timing, wherebyit works to low-rate transfer the shared data “STN31DataL” as stored atthe address 62 in the shared memory area (as the global shared memoryarea 51 a) to whole stations STN11 to STN1 n connected to the networkN1. And, the stations STN11 to STN1 n each respectively have thetransferred shared data “STN31DataL” stored at an address 62 set in alow transfer rate block 38 of the shared memory area (as the globalshared memory area 50 a).

It therefore is possible for the control device PCS11 to read the data“STN31DataL” transferred to the station STN11 in the network N1.

It is noted that in the example illustrated in FIG. 7 the data transfersystem DT5 as well as DT6 has a combination of stations directlyconnected thereto as a first station and a second station. That is, tothe data transfer system DT5, connected is a combination of stationSTN11 as a first station, and station STN21 as a second station. Alsofor the data transfer system DT6, connected thereto is a combination ofstation STN21 as a first station, and station STN31 as a second station

For the data transfer system DT5, letting the station STN11 be a firststation connected thereto, and the station STN21 be a second station,the station STN11 has a shared memory area (as a global shared memoryarea 50 a) corresponding to a first memory element, the station STN21having a shared memory area (as a global shared memory area 54 a)corresponding to a second memory element, the data transfer system DT5having a shared memory area (as a global shared memory area 51 a)corresponding to a third memory element, the data transfer system DT5having a shared memory area (as a global shared memory area 53 a)corresponding to a fourth memory element.

According to the second embodiment, the network control system 1 b isadapted in addition to effects of the network control system 1 accordingto the first embodiment, to have a plurality of transfer rates set fortransfer of shared data among networks, allowing for an enhancedefficiency in use of the networks.

Third Embodiment

Description is now made of a network control system 1 c according to athird embodiment.

FIG. 8 is an explanatory diagram showing an example of global sharedmemory area 11 set up as an array of consecutive areas from a beginningaddress.

As illustrated in FIG. 8, there is an array of consecutive areas set asa global shared memory area 11, to thereby implement a data transfersystem between networks with an increased data transfer rate. In thisrespect, simply with an enabled setup of an array of consecutive areas,there might appear inconveniences in extension or modification of globalshared memory area 11 by users.

To this point, according to the third embodiment, the network controlsystem 1 c is configured for adaptation to set up a global shared memoryarea 11 using an arbitrary subset of a set of areas in a network sharedmemory space, in a voluntary manner.

FIG. 9 is a configuration diagram showing a system configuration of thenetwork control system 1 c according to the third embodiment.

As illustrated in FIG. 9, the network control system 1 c according tothe third embodiment includes, besides a configuration of networkcontrol system 1 according to the first embodiment, an engineeringsystem 63 configured with a memory area (as a global shared memory area11) shared to be common among whole networks, to download settingsthereof to respective stations STN and data transfer systems DT1 andDT2.

The engineering system 63 has the memory area (as the global sharedmemory area 11) set up to share among whole networks N1, N2, and N3. Theengineering system 63 is connected to the network N1, and has itssetting values downloaded to whole stations STN11 to STN1 n in thenetwork N1 and the data transfer system DT1. The data transfer systemDT1 works to transfer the downloaded setting values to the network N2,whereby the setting values are downloaded to whole stations STN21 toSTN2 n in the network N2 and the data transfer system DT2.

The data transfer system DT2 works to transfer the downloaded settingvalues to the network N3, whereby the setting values are downloaded towhole stations STN31 to STN3 n in the network N3.

And, the data transfer system DT1 has a global shared memory area 11 setup in an arbitrary subset of a set of areas in a network shared memoryspace thereof in accordance with shared setting information.

FIG. 10 is an explanatory diagram showing an example of global sharedmemory area set up with memory areas according to shared settinginformation.

As illustrated in FIG. 10, the network control system 1 c according tothe third embodiment is adapted to have a global shared memory area 11set up in an arbitrary subset of a set of areas in a network sharedmemory space in a voluntary manner, allowing for efficient utilizationof the global shared memory area 11 being shared among the wholenetworks.

The engineering system 63 is connected to the network N1 in aconfiguration shown by the configuration diagram in FIG. 9, while thisconfiguration is not restrictive. For instance, there may be aconfiguration including an engineering system 63 individually connectedto respective stations and data transfer systems each adapted todownload setting values as setting information to be shared.

Fourth Embodiment

FIG. 11 is a configuration diagram showing a system configuration of anetwork control system 1 d according to a fourth embodiment.

As shown in FIG. 11, the network control system 1 d according to thefourth embodiment includes a data transfer system DT7 configured toimplement transfer of data among whole networks, substituting for thecombination of data transfer systems DT1 and DT2 in configuration of thenetwork control system 1 according to the first embodiment.

FIG. 12 is a configuration diagram showing a hardware configuration ofthe data transfer system DT7 in the network control system 1 d accordingto the fourth embodiment.

As shown in FIG. 12, in the network control system 1 d according to thefourth embodiment, the data transfer system DT7 includes a combinationof T/R's 21, 29, and 76 configured as transmitter receiver sets, acombination of MAC's 22, 30, and 77 configured as medium accesscontrollers, a combination of ARB's 23, 31, and 78 configured as bustraffic arbitrators, a CM 67 configured as a common memory shared in anetwork N1, a CM 69 configured as a common memory shared in a networkN2, a CM 71 configured as a common memory shared in a network N3, a DMA25, an MPU 26 configured for central control, an I/F 27 configured as atransfer parameter in-taking interface, an FROM 28 configured as atransfer parameter memory, a combination of CNT's 90, 92, and 94configured as transfer controllers, and a combination of WAT's 91, 93,and 95 configured as transfer period monitors.

The CM 67 is divided, like the shared memory 2 illustrated in FIG. 1(a), into an area set up as (a global shared memory area 67 a) beingsharable to be common among the networks N1 to N3, and an area set up as(a local shared memory area 67 b) being effective simply within thenetwork N1.

The CM 69 is divided, like the shared memory 3 illustrated in FIG. 1(a), into an area set up as (a global shared memory area 69 a) beingshamble to be common among the networks N1 to N3, and an area set up as(a local shared memory area 69 b) being effective simply within thenetwork N2.

The CM 71 is divided, like the shared memory 4 illustrated in FIG. 1(a), into an area set up as (a global shared memory area 71 a) beingsharable to be common among the networks N1 to N3, and an area set up as(a local shared memory area 71 b) being effective simply within thenetwork N3.

The CNT 90 is configured to determine a first transfer period as atransfer period in transfer of shared data from the data transfer systemDT7 to stations STN11 to STN1 n.

The WAT 91 is configured to work in accordance with the first transferperiod determined by the CNT 90, to detect a time point of transfer ofshared data from the data transfer system DT7 to stations STN11 to STN1n, as a second transfer timing. Further, the WAT 91 is configured todetect a time point of reception of shared data from any of stationsSTN21 to STN2 n and stations STN31 to STN3 n to the data transfer systemDT7, as a first transfer timing to be a time point earlier than thesecond transfer timing by a prescribed time interval. And, the WAT 91 isadapted to work upon detection of the first transfer timing or thesecond transfer timing, to supply the MPU 26 with a signal representingthe detection.

The CNT 92 is configured to determine a second transfer period as atransfer period in transfer of shared data from the data transfer systemDT7 to stations STN21 to STN2 n.

The WAT 93 is configured to work in accordance with the second transferperiod determined by the CNT 92, to detect a time point of transfer ofshared data from the data transfer system DT7 to stations STN21 to STN2n, as a fourth transfer timing. Further, the WAT 93 is configured todetect a time point of reception of shared data from any of stationsSTN11 to STN1 n and stations STN31 to STN3 n to the data transfer systemDT7, as a third transfer timing to be a time point earlier than thefourth transfer timing by a prescribed time interval. And, the WAT 93 isadapted to work upon detection of the third transfer timing or thefourth transfer timing, to supply the MPU 26 with a signal representingthe detection.

The CNT 94 is configured to determine a third transfer period as atransfer period in transfer of shared data from the data transfer systemDT7 to stations STN31 to STN3 n.

The WAT 95 is configured to work in accordance with the third transferperiod determined by the CNT 94, to detect a time point of transfer ofshared data from the data transfer system DT7 to stations STN31 to STN3n, as a sixth transfer timing. Further, the WAT 95 is configured todetect a time point of reception of shared data from any of stationsSTN11 to STN1 n and stations STN21 to STN2 n to the data transfer systemDT7, as a fifth transfer timing to be a time point earlier than thesixth transfer timing by a prescribed time interval. And, the WAT 95 isadapted to work upon detection of the fifth transfer timing or the sixthtransfer timing, to supply the MPU 26 with a signal representing thedetection.

Further, the FROM 28 has stored therein pieces of information on sharedmemories as targets of global shared memories on the networks. Morespecifically, the FROM 28 has stored therein sets of addresses of globalmemory areas and directions data transfer associated therewith, asinformation on shared memories.

Such pieces of information on shared memories are stored in the FROM 28from an external interface, through the I/F 27 configured as a transferparameter in-taking interface, and the MPU 26. Also, there may be piecesof information on shared memories taken in as targets of global sharedmemories, through the network N1, the network N2, or the network N3.

Functionally, the MPU 26 is configured with a first transfer means 26 a,a second transfer means 26 b, and a third transfer means 26 c. And, thefirst transfer means 26 a, the second transfer means 26 b, and the thirdtransfer means 26 c are each adapted to read pieces of information onglobal shared memories in the FROM 28, to make the following controlactions in accordance with read information on setting.

At the MPU 26, the first transfer means 26 a is adapted to operate inaccordance with a first transfer period determined by the CNT 90, tohave pieces of shared data as stored in global shared memory areas ofstations STN21 to STN2 n and stations STN31 to STN3 n, stored in globalshared memory areas of the CM 69 and the CM 71, respectively, withaddresses identical to their addresses in those global shared memoryareas.

More specifically, the first transfer means 26 a operates, at a firsttransfer timing, to store in the CM 69 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31. Further, the first transfer means 26 a operates, at thefirst transfer timing, to store in the CM 71 those pieces of shared datareceived from the network N3, by employing the T/R 76, the MAC 77, andthe ARB 78.

Further, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a second transfer period determined by theCNT 92, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN1 n and stations STN31 to STN3 n, storedin global shared memory areas of the CM 67 and the CM 71, respectively,with addresses identical to their addresses in those global sharedmemory areas.

More specifically, the first transfer means 26 a operates, at a thirdtransfer timing, to store in the CM 67 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23. Further, the first transfer means 26 a operates, at thethird transfer timing, to store in the CM 71 those pieces of shared datareceived from the network N3, by employing the T/R 76, the MAC 77, andthe ARB 78.

Still more, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a third transfer period determined by the CNT94, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN1 n and stations STN21 to STN2 n, storedin global shared memory areas of the CM 67 and the CM 69, respectively,with addresses identical to their addresses in those global sharedmemory areas.

More specifically, the first transfer means 26 a operates, at a fifthtransfer timing, to store in the CM 67 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23. Further, the first transfer means 26 a operates, at thefifth transfer timing, to store in the CM 69 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31.

At the MPU 26, the second transfer means 26 b is adapted to operate, asthe CM 67 has pieces of shared data stored in a global shared memoryarea thereof by the first transfer means 26 a, to store the pieces ofshared data in the global shared memory areas of the CM 69 and the CM71, with addresses identical to their addresses in the global sharedmemory area of the CM 67.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 67, stored in a global shared memory area of the CM 69, by employingthe ARB 23, the DMA 25, and the ARB 31. Further, the second transfermeans 26 b operates to have pieces of shared data as stored in theglobal shared memory area of the CM 69, stored in a global shared memoryarea of the CM 71, by employing the ARB 31, the DMA 25, and the ARB 78.

Further, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 69 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory areas of the CM 67 and the CM71, with addresses identical to their addresses in the global sharedmemory area of the CM 69.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 69, stored in the global shared memory area of the CM 67, byemploying the ARB 31, the DMA 25, and the ARB 23. Further, the secondtransfer means 26 b operates to have pieces of shared data as stored inthe global shared memory area of the CM 69, stored in a global sharedmemory area of the CM 71, by employing the ARB 31, the DMA 25, and theARB 78.

Still more, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 71 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory areas of the CM 67 and the CM69, with addresses identical to their addresses in the global sharedmemory area of the CM 71.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 71, stored in the global shared memory area of the CM 67, byemploying the ARB 78, the DMA 25, and the ARB 23. Further, the secondtransfer means 26 b operates to have pieces of shared data as stored inthe global shared memory area of the CM 71, stored in the global sharedmemory area of the CM 69, by employing the ARB 78, the DMA 25, and theARB 31.

At the MPU 26, the third transfer means 26 c is adapted to operate inaccordance with a first transfer period supplied from the WAT 91, tohave pieces of shared data as stored in the global shared memory area ofthe CM 67, stored in global shared memory areas of stations STN11 toSTN1 n, with addresses identical to their addresses in the global sharedmemory area of the CM 67.

More specifically, the third transfer means 26 c operates, at a secondtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 67, stored in the global shared memoryareas of stations STN11 to STN1 n, by employing the ARB 23, the MAC 22,and the T/R 21.

Further, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a second transfer period supplied from theWAT 93, to have pieces of shared data as stored in the global sharedmemory area of the CM 69, stored in global shared memory areas ofstations STN21 to STN2 n, with addresses identical to their addresses inthe global shared memory area of the CM 69.

More specifically, the third transfer means 26 c operates, at a fourthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 69, stored in the global shared memoryareas of stations STN21 to STN2 n, by employing the ARB 31, the MAC 30,and the T/R 29.

Still more, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a third transfer period supplied from the WAT95, to have pieces of shared data as stored in the global shared memoryarea of the CM 71, stored in global shared memory areas of stationsSTN31 to STN3 n, with addresses identical to their addresses in theglobal shared memory area of the CM 71.

More specifically, the third transfer means 26 c operates, at a sixthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 71, stored in the global shared memoryareas of stations STN31 to STN3 n, by employing the ARB 78, the MAC 77,and the T/R 76.

Description is now made of actions of the network control system 1 daccording to the fourth embodiment of the present invention, withreference to FIG. 13.

FIG. 13 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 d according tothe fourth embodiment of the present invention.

In FIG. 13, there is a set of stations STN11 to STN1 n connected to thenetwork N1, of which a single station STN11 is depicted for simplifieddescription. Likewise, there is a set of stations STN21 to STN2 nconnected to the network N2, of which a single station STN21 isdepicted, there being a set of stations STN31 to STN3 n connected to thenetwork N3, of which a single station STN31 is depicted.

As illustrated in FIG. 13, the data transfer system DT7 is provided withmemories shared to be common. Each shared memory is divided into, to setup, a global shared memory area shamble to be common among the networksN1, N2, and N3, and a local shared memory area effective simply within acorresponding one of the networks.

Further, though being not depicted, there is a combination of n stationsSTN11 to STN1 n, n stations STN21 to STN2 n, and n stations STN31 toSTN3 n each respectively including a memory likewise shared, the sharedmemory being divided into, to set up, a global shared memory areasharable to be common among the networks N1, N2, and N3, and a localshared memory area effective simply within a corresponding one of thenetworks.

There comes transfer of shared data to stations STN11 to STN with atransfer period referred herein to as a first transfer period, therecoming transfer of shared data to stations STN21 to STN2 n with atransfer period referred herein to as a second transfer period, andtransfer of shared data to stations STN31 to STN3 n with a transferperiod referred herein to as a third transfer period.

And, the data transfer system DT7 is adapted to work in accordance withthe first transfer period, to detect a first transfer timing as a timepoint of reception of shared data from stations STN21 to STN2 n andstations STN31 to STN3 n to the data transfer system DT7, and a secondtransfer timing as a time point of transfer of shared data from the datatransfer system DT7 to stations STN11 to STN1 n.

Further, the data transfer system DT7 is adapted to work in accordancewith the second transfer period, to detect a third transfer timing as atime point of reception of shared data from stations STN11 to STN1 n andstations STN31 to STN3 n to the data transfer system DT7, and a fourthtransfer timing as a time point of transfer of shared data from the datatransfer system DT7 to stations STN21 to STN2 n.

Still more, the data transfer system DT7 is adapted to work inaccordance with the third transfer period, to detect a fifth transfertiming as a time point of reception of shared data from stations STN11to STN1 n and stations STN21 to STN2 n to the data transfer system DT7,and a sixth transfer timing as a time point of transfer of shared datafrom the data transfer system DT7 to stations STN31 to STN3 n.

Description is now first made of actions of the network control system 1d along with operation of a control device PCS11 connected with astation STN11 in the network N1 to update a piece of shared data storedin global shared memory areas.

As shown in FIG. 13, in the network N1, a control device PCS11 connectedwith the station STN11 writes a data “STN11Data” at an address 64 (notdepicted) in a shared memory area (as a global shared memory area) ofthe station STN11, whereby the station STN11 works to transfer thewritten data “STN11Data” to a whole of stations STN12 to STN1 n in thenetwork N1 with the data transfer system DT7 inclusive.

And, the data transfer system DT7 detects a third transfer timing or afifth transfer timing, whereby it works to receive the transferredshared data “STN11Data”, and store the received shared data “STN11Data”at an address 64 in a shared memory area (as a global shared memory area67 a) in the CM 67.

Next, the data transfer system DT7 works to have the shared data“STN11Data”, as it is stored at the address 64 in the shared memory area(as the global shared memory area 67 a), stored at an address 64 in ashared memory area (as a global shared memory area 69 a) thereof.Further, the data transfer system DT7 works to have the shared data“STN11Data”, as it is stored at the address 64 in the shared memory area(as the global shared memory area 69 a), stored at an address 64 in ashared memory area (as a global shared memory area 71 a) thereof.

The data transfer system DT7 detects a fourth transfer timing, wherebyit works to transfer the shared data “STN11Data” as stored at theaddress 64 in the shared memory area (as the global shared memory area69 a) to whole stations STN21 to STN2 n (FIG. 13 simply depicts thestation STN21) connected to the network N2. And, the stations STN21 toSTN2 n each respectively have the transferred shared data “STN11Data”stored at an address 64 (not depicted) in a shared memory area (as aglobal shared memory area) thereof.

Further, the data transfer system DT7 detects a sixth transfer timing,whereby it works to transfer the shared data “STN11Data” as stored atthe address 64 in the shared memory area (as the global shared memoryarea 71 a) to whole stations STN31 to STN3 n (FIG. 13 simply depicts thestation STN31) connected to the network N3. And, the stations STN31 toSTN3 n each respectively have the transferred shared data “STN11Data”stored at an address 64 (not depicted) in a shared memory area (as aglobal shared memory area) thereof.

It therefore is possible for a control device PCS21 to read the data“STN11Data” transferred to the station STN21 in the network N2, and forthe control device PCS31 to read the data “STN11Data” transferred to thestation STN31 in the network N3.

Description is now made of actions of the network control system 1 dalong with operation of a control device PCS31 connected with a stationSTN11 in the network N3 to update a piece of shared data stored inglobal shared memory areas.

As shown in FIG. 13, in the network N3, the control device PCS31connected with the station STN31 writes a data “STN31Data” at an address66 (not depicted) in a shared memory area (as a global shared memoryarea) of the station STN11, whereby the station STN11 works to transferthe written data “STN31Data” to a whole of stations STN32 to STN3 n inthe network N3 with the data transfer system DT7 inclusive.

And, the data transfer system DT7 detects a first transfer timing or athird transfer timing, whereby it works to receive the transferredshared data “STN31Data”, and store the received shared data “STN31Data”at an address 66 in the shared memory area (as the global shared memoryarea 71 a).

Next, the data transfer system DT7 works to have the shared data“STN31Data”, as it is stored at the address 66 in the shared memory area(as the global shared memory area 71 a), stored at an address 66 in theshared memory area (as the global shared memory area 69 a). Further, thedata transfer system DT7 works to have the shared data “STN31Data”, asit is stored at the address 66 in the shared memory area (as the globalshared memory area 69 a), stored at an address 66 in the shared memoryarea (as the global shared memory area 67 a).

The data transfer system DT7 detects a fourth transfer timing, wherebyit works to transfer the shared data “STN31Data” as stored at theaddress 66 in the shared memory area (as the global shared memory area69 a) to whole stations STN21 to STN2 n (FIG. 13 simply depicts thestation STN21) connected to the network N2. And, the stations STN21 toSTN2 n each respectively have the transferred shared data “STN31Data”stored at an address 66 (not depicted) in a shared memory area (as aglobal shared memory area) thereof.

Further, the data transfer system DT7 detects a second transfer timing,whereby it works to transfer the shared data “STN31Data” as stored atthe address 66 in the shared memory area (as the global shared memoryarea 67 a) to whole stations STN11 to STN1 n (FIG. 13 simply depicts thestation STN11) connected to the network N1. And, the stations STN11 toSTN1 n each respectively have the transferred shared data “STN31Data”stored at an address 66 (not depicted) in a shared memory area (as aglobal shared memory area) thereof.

It therefore is possible for the control device PCS21 to read the data“STN31Data” transferred to the station STN11 in the network N1, and forthe control device PCS21 to read the data “STN31Data” transferred to thestation STN21 in the network N2.

Such being the case, the data transfer system DT7 is adapted to work fordata transfer in accordance with a transfer period of a network at adestination of transfer, affording to eliminate repetition of transferof a shared data, thus always allowing for transfer of fresh shareddata.

As is apparent from the foregoing, according to the fourth embodiment,the network control system 1 d permits concentration of data transfersystem and reduction of installation place, thus allowing for efficientutilization of global memory areas, with a reduce cost.

Further, the data transfer system DT7 affords to transfer stored data inglobal memory areas thereof to networks, permitting high-rate transferof data without transfer delays, even with an increased number ofnetworks connected to the data transfer system DT7.

Fifth Embodiment

There is a network control system according to a fifth embodiment of thepresent invention that includes a data transfer system connected tonetworks N1 to N3, to implement transfer of data among the networks N1to N3, like the network control system 1 d according to the fourthembodiment of the present invention.

Further, in the network control system according to the fifth embodimentof the present invention, the networks N1 to N3 include stations thereofhaving their shared memories each divided into sub-areas, by orders ofpriority of shared data. More specifically, like the network controlsystem 1 b according to the second embodiment, each shared memory in thenetwork N1 is divided into classes of transfer rate as set up in threeranks being a high transfer rate block 36, a medium transfer rate block37, and a low transfer rate block 38. Also in the network N2, eachshared memory is divided into prioritized classes likewise set up inthree ranks, as well as each shared memory in the network N3.

FIG. 14 is a configuration diagram showing a hardware configuration ofthe data transfer system DT8 in the network control system 1 e accordingto the fifth embodiment.

As shown in FIG. 14, in the network control system 1 e according to thefifth embodiment, the data transfer system DT8 includes a combination ofT/R's 21, 29, and 76 configured as transmitter receiver sets, acombination of MAC's 22, 30, and 77 configured as medium accesscontrollers, a combination of ARB's 23, 31, and 78 configured as bustraffic arbitrators, a CM 80 configured as a common memory shared in thenetwork N1, a CM 82 configured as a common memory shared in the networkN2, a CM 84 configured as a common memory shared in the network N3, aDMA 25, an MPU 26 configured for central control, an I/F 27 configuredas a transfer parameter in-taking interface, an FROM 28 configured as atransfer parameter memory, a combination of CNT's 90, 92, and 94configured as transfer controllers, and a combination of WAT's 91, 93,and 95 configured as transfer period monitors.

The CM 80 is divided, like the shared memory 50 illustrated in FIG. 5(a), into an area set up as (a global shared memory area 80 a) beingshamble to be common among the networks N1 to N3, and an area set up as(a local shared memory area 80 b) being effective simply within thenetwork N1. Further, the global shared memory area is divided intosub-areas, by orders of priority of shared data, like the shared memory50 illustrated in FIG. 5( a). More specifically, the global sharedmemory area is divided into classes of transfer rate as set up in threeranks being a high transfer rate block 36, a medium transfer rate block37, and a low transfer rate block 38.

The CM 82 is divided, like the shared memory 54 illustrated in FIG. 5(a), into an area set up as (a global shared memory area 82 a) beingshamble to be common among the networks N1 to N3, and an area set up as(a local shared memory area 82 b) being effective simply within thenetwork N2. Further, the global shared memory area is divided intosub-areas, by orders of priority of shared data, like the shared memory54 illustrated in FIG. 5( a). More specifically, the global sharedmemory area is divided into classes of transfer rate as set up in threeranks being a high transfer rate block 36, a medium transfer rate block37, and a low transfer rate block 38.

The CM 84 is divided, like a shared memory 58 illustrated in FIG. 5( a),into an area set up as (a global shared memory area 84 a) being sharableto be common among the networks N1 to N3, and an area set up as (a localshared memory area 84 b) being effective simply within the network N3.Further, the global shared memory area is divided into sub-areas, byorders of priority of shared data, like the shared memory 58 illustratedin FIG. 5( a). More specifically, the global shared memory area isdivided into classes of transfer rate as set up in three ranks being ahigh transfer rate block 36, a medium transfer rate block 37, and a lowtransfer rate block 38.

There is a PRI 49 configured to store therein, as pieces of informationon order of priority, respective orders of priorities in transfer ofshared data between the data transfer system DT8 and sets of stationsSTN11 to STN1 n, stations STN21 to STN2 n, and stations STN31 to STN3 n.The priority order information stored includes sets of addresses ofglobal shared memory areas and associated orders of priorities eachrepresenting a high rate, a medium rate, or a low rate.

The CNT 90 is configured to read a piece of information on order ofpriority from the PRI 149, and work on the basis of priority orderinformation, to determine a first transfer period as a transfer periodin transfer of shared data from the data transfer system DT8 to stationsSTN11 to STN1 n. More specifically, the CNT 90 selects a transfer periodaccording to the priority order information representing a high rate, amedium rate, or a low rate, to provide the selected transfer period as afirst transfer period.

The WAT 91 is configured to work in accordance with the first transferperiod determined by the CNT 90, to detect a time point of transfer ofshared data from the data transfer system DT8 to stations STN11 to STN1n, as a second transfer timing. Further, the WAT 91 is configured todetect a time point of reception of shared data from any of stationsSTN21 to STN2 n and stations STN31 to STN3 n to the data transfer systemDT8, as a first transfer timing to be a time point earlier than thesecond transfer timing by a prescribed time interval. And, the WAT 91 isadapted to work upon detection of the first transfer timing or thesecond transfer timing, to supply the MPU 26 with a signal representingthe detection.

The CNT 92 is configured to read a piece of information on order ofpriority from the PRI 149, and work on the basis of information onpriority order, to determine a second transfer period as a transferperiod in transfer of shared data from the data transfer system DT8 tostations STN21 to STN2 n. More specifically, the CNT 92 selects atransfer period according to the priority order information representinga high rate, a medium rate, or a low rate, to provide the selectedtransfer period as a second transfer period.

The WAT 93 is configured to work in accordance with the second transferperiod determined by the CNT 92, to detect a time point of transfer ofshared data from the data transfer system DT8 to stations STN21 to STN2n, as a fourth transfer timing. Further, the WAT 93 is configured todetect a time point of transfer of shared data from any of stationsSTN11 to STN1 n and stations STN31 to STN3 n to the data transfer systemDT8, as a third transfer timing to be a time point earlier than thefourth transfer timing by a prescribed time interval. And, the WAT 93 isadapted to work upon detection of the third transfer timing or thefourth transfer timing, to supply the MPU 26 with a signal representingthe detection.

The CNT 94 is configured to read a piece of information on order ofpriority from the PRI 149, and work on the basis of information onpriority order, to determine a third transfer period as a transferperiod in transfer of shared data from the data transfer system DT8 tostations STN31 to STN3 n. More specifically, the CNT 94 selects atransfer period according to the priority order information representinga high rate, a medium rate, or a low rate, to provide the selectedtransfer period as a third transfer period.

The WAT 95 is configured to work in accordance with the third transferperiod determined by the CNT 94, to detect a time point of transfer ofshared data from the data transfer system DT8 to stations STN31 to STN3n, as a sixth transfer timing. Further, the WAT 95 is configured todetect a time point of transfer of shared data from any of stationsSTN11 to STN1 n and stations STN21 to STN2 n to the data transfer systemDT8, as a fifth transfer timing to be a time point earlier than thesixth transfer timing by a prescribed time interval. And, the WAT 95 isadapted to work upon detection of the fifth transfer timing or the sixthtransfer timing, to supply the MPU 26 with a signal representing thedetection.

Functionally, the MPU 26 is configured with a first transfer means 26 a,a second transfer means 26 b, and a third transfer means 26 c. And, thefirst transfer means 26 a, the second transfer means 26 b, and the thirdtransfer means 26 c are each adapted to read pieces of information onglobal shared memories in the FROM 28, to make the following controlactions in accordance with read information on setting.

At the MPU 26, the first transfer means 26 a is adapted to operate inaccordance with a first transfer period determined by the CNT 90, tohave pieces of shared data as stored in global shared memory areas ofstations STN21 to STN2 n and stations STN31 to STN3 n, stored in globalshared memory areas of the CM 82 and the CM 84, respectively, withaddresses identical to their addresses in those global shared memoryareas.

More specifically, the first transfer means 26 a operates, at a firsttransfer timing, to store in the CM 82 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31. Further, the first transfer means 26 a operates, at thefirst transfer timing, to store in the CM 84 those pieces of shared datareceived from the network N3, by employing the T/R 76, the MAC 77, andthe ARB 78.

Further, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a second transfer period determined by theCNT 92, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN and stations STN31 to STN3 n, stored inglobal shared memory areas of the CM 80 and the CM 84, respectively,with addresses identical to their addresses in those global sharedmemory areas.

More specifically, the first transfer means 26 a operates, at a thirdtransfer timing, to store in the CM 80 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23. Further, the first transfer means 26 a operates, at thethird transfer timing, to store in the CM 84 those pieces of shared datareceived from the network N3, by employing the T/R 76, the MAC 77, andthe ARB 78.

Still more, at the MPU 26, the first transfer means 26 a is adapted tooperate in accordance with a third transfer period determined by the CNT94, to have pieces of shared data as stored in global shared memoryareas of stations STN11 to STN1 n and stations STN21 to STN2 n, storedin global shared memory areas of the CM 80 and the CM 82, respectively,with addresses identical to their addresses in those global sharedmemory areas.

More specifically, the first transfer means 26 a operates, at a fifthtransfer timing, to store in the CM 80 those pieces of shared datareceived from the network N1, by employing the T/R 21, the MAC 22, andthe ARB 23. Further, the first transfer means 26 a operates, at thefifth transfer timing, to store in the CM 82 those pieces of shared datareceived from the network N2, by employing the T/R 29, the MAC 30, andthe ARB 31.

At the MPU 26, the second transfer means 26 b is adapted to operate, asthe CM 80 has pieces of shared data stored in a global shared memoryarea thereof by the first transfer means 26 a, to store the pieces ofshared data in the global shared memory areas of the CM 82 and the CM84, with addresses identical to their addresses in the global sharedmemory area of the CM 80.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 80, stored in a global shared memory area of the CM 82, by employingthe ARB 23, the DMA 25, and the ARB 31. Further, the second transfermeans 26 b operates to have pieces of shared data as stored in theglobal shared memory area of the CM 82, stored in a global shared memoryarea of the CM 84, by employing the ARB 31, the DMA 25, and the ARB 78.

Further, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 82 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory areas of the CM 80 and the CM784, with addresses identical to their addresses in the global sharedmemory area of the CM 82.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 82, stored in the global shared memory area of the CM 80, byemploying the ARB 31, the DMA 25, and the ARB 23. Further, the secondtransfer means 26 b operates to have pieces of shared data as stored inthe global shared memory area of the CM 82, stored in a global sharedmemory area of the CM 84, by employing the ARB 31, the DMA 25, and theARB 78.

Still more, at the MPU 26, the second transfer means 26 b is adapted tooperate, as the CM 84 has pieces of shared data stored in the globalshared memory area by the first transfer means 26 a, to store the piecesof shared data in the global shared memory areas of the CM 80 and the CM82, with addresses identical to their addresses in the global sharedmemory area of the CM 84.

More specifically, the second transfer means 26 b operates to havepieces of shared data as stored in the global shared memory area of theCM 84, stored in the global shared memory area of the CM 80, byemploying the ARB 78, the DMA 25, and the ARB 23. Further, the secondtransfer means 26 b operates to have pieces of shared data as stored inthe global shared memory area of the CM 84, stored in the global sharedmemory area of the CM 82, by employing the ARB 78, the DMA 25, and theARB 31.

At the MPU 26, the third transfer means 26 c is adapted to operate inaccordance with a first transfer period supplied from the WAT 91, tohave pieces of shared data as stored in the global shared memory area ofthe CM 80, stored in global shared memory areas of stations STN11 toSTN1 n, with addresses identical to their addresses in the global sharedmemory area of the CM 80.

More specifically, the third transfer means 26 c operates, at a secondtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 80, stored in the global shared memoryareas of stations STN11 to STN1 n, by employing the ARB 23, the MAC 22,and the T/R 21.

Further, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a second transfer period supplied from theWAT 93, to have pieces of shared data as stored in the global sharedmemory area of the CM 82, stored in global shared memory areas ofstations STN21 to STN2 n, with addresses identical to their addresses inthe global shared memory area of the CM 82.

More specifically, the third transfer means 26 c operates, at a fourthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 82, stored in the global shared memoryareas of stations STN21 to STN2 n, by employing the ARB 31, the MAC 30,and the T/R 29.

Still more, at the MPU 26, the third transfer means 26 c is adapted tooperate in accordance with a third transfer period supplied from the WAT95, to have pieces of shared data as stored in the global shared memoryarea of the CM 84, stored in global shared memory areas of stationsSTN31 to STN3 n, with addresses identical to their addresses in theglobal shared memory area of the CM 84.

More specifically, the third transfer means 26 c operates, at a sixthtransfer timing, to have pieces of shared data as stored in the globalshared memory area of the CM 84, stored in the global shared memoryareas of stations STN31 to STN3 n, by employing the ARB 78, the MAC 77,and the T/R 76.

Description is now made of actions of the network control system 1 eaccording to the fifth embodiment of the present invention, withreference to FIG. 15.

FIG. 15 is a diagram describing data transfer of shared data amongnetworks N1, N2, and N3 in the network control system 1 e according tothe fifth embodiment of the present invention.

In FIG. 15, there is a set of stations STN11 to STN1 n connected to thenetwork N1, of which a single station STN11 is depicted for simplifieddescription. Likewise, there is a set of stations STN21 to STN2 nconnected to the network N2, of which a single station STN21 isdepicted, there being a set of stations STN31 to STN3 n connected to thenetwork N3, of which a single station STN31 is depicted.

As illustrated in FIG. 15, the data transfer system DT8 includes theCM's 80, 82, and 84 as memories shared to be common. Each shared memoryis divided into, to set up, a global shared memory area sharable to becommon among the networks N1, N2, and N3, and a local shared memory areaeffective simply within a corresponding one of the networks.

Further, though being not depicted, there is a combination of n stationsSTN11 to STN1 n, n stations STN21 to STN2 n, and n stations STN31 toSTN3 n each respectively including a memory likewise shared, the sharedmemory being divided into, to set up, a global shared memory areashamble to be common among the networks N1, N2, and N3, and a localshared memory area effective simply within a corresponding one of thenetworks.

There comes transfer of shared data to stations STN11 to STN1 n with atransfer period referred herein to as a first transfer period, therecoming transfer of shared data to stations STN21 to STN2 n with atransfer period referred herein to as a second transfer period, andtransfer of shared data to stations STN31 to STN3 n with a transferperiod referred herein to as a third transfer period. The first transferperiod is determined in correspondence to a piece of information onpriority order representing a high rate, a medium rate, or a low rate.Likewise, the second transfer period and the third transfer period alsoare each determined in correspondence to a piece of information onpriority order representing a high rate, a medium rate, or a low rate.

And, the data transfer system DT8 is adapted to work in accordance withthe first transfer period, to detect a first transfer timing as a timepoint of reception of shared data from stations STN21 to STN2 n andstations STN31 to STN3 n to the data transfer system DT8, and a secondtransfer timing as a time point of transfer of shared data from the datatransfer system DT8 to stations STN11 to STN1 n.

Further, the data transfer system DT8 is adapted to work in accordancewith the second transfer period, to detect a third transfer timing as atime point of reception of shared data from stations STN11 to STN1 n andstations STN31 to STN3 n to the data transfer system DT8, and a fourthtransfer timing as a time point of transfer of shared data from the datatransfer system DT8 to stations STN21 to STN2 n.

Still more, the data transfer system DT8 is adapted to work inaccordance with the third transfer period, to detect a fifth transfertiming as a time point of reception of shared data from stations STN11to STN1 n and stations STN21 to STN2 n to the data transfer system DT8,and a sixth transfer timing as a time point of transfer of shared datafrom the data transfer system DT8 to stations STN31 to STN3 n.

Description is now first made of actions of the network control system 1e along with operation for a control device PCS11 connected with astation STN11 in the network N1 to update a piece of shared data storedin global shared memory areas.

As shown in FIG. 15, in the network N1, the control device PCS11connected with the station STN11 writes a data “STN11DataH” at anaddress 96 (not depicted) in a high transfer rate block 36 of a sharedmemory area (as a global shared memory area) of the station STN11,whereby the station STN11 works to high-rate transfer the written data“STN11DataH” to a whole of stations STN12 to STN1 n in the network N1with the data transfer system DT8 inclusive.

And, the data transfer system DT8 detects a third transfer timing or afifth transfer timing, whereby it works to receive the transferredshared data “STN11DataH”, and store the received shared data“STN11DataH” at an address 96 in a high transfer rate block 36 of ashared memory area (as a global shared memory area 80 a) thereof.

Next, the data transfer system DT8 works to have the shared data“STN11DataH”, as it is stored at the address 96 in the shared memoryarea (as the global shared memory area 80 a), stored at an address 96 ina high transfer rate block 36 of a shared memory area (as a globalshared memory area 82 a) thereof. Further, the data transfer system DT8works to have the shared data “STN11DataH”, as it is stored at theaddress 96 in the shared memory area (as the global shared memory area82 a), stored at an address 96 in a high transfer rate block 36 of ashared memory area (as a global shared memory area 84 a) thereof.

The data transfer system DT8 detects a fourth transfer timing, wherebyit works to high-rate transfer the shared data “STN11DataH” as stored atthe address 96 in the high transfer rate block 36 of the shared memoryarea (as the global shared memory area 82 a) to whole stations STN21 toSTN2 n (FIG. 15 simply depicts the station STN21) connected to thenetwork N2. And, the stations STN21 to STN2 n each respectively have thetransferred shared data “STN11DataH” stored at an address 96 (notdepicted) in a shared memory area (as a global shared memory area)thereof.

Further, the data transfer system DT8 detects a sixth transfer timing,whereby it works to high-rate transfer the shared data “STN11DataH” asstored at the address 96 in the high transfer rate block 36 of theshared memory area (as the global shared memory area 84 a) to wholestations STN31 to STN3 n (FIG. 15 simply depicts the station STN31)connected to the network N3. And, the stations STN31 to STN3 n eachrespectively have the transferred shared data “STN11DataH” stored at anaddress 96 (not depicted) in a high transfer rate block 36 of a sharedmemory area (as a global shared memory area) thereof.

It therefore is possible for a control device PCS21 to read the data“STN11DataH” transferred to the station STN21 in the network N2, and fora control device PCS31 to read the data “STN11DataH” transferred to thestation STN31 in the network N3.

Description is now made of actions of the network control system 1 ealong with operation for a control device PCS31 connected with a stationSTN31 in the network N3 to update a piece of shared data stored inglobal shared memory areas.

As shown in FIG. 15, in the network N3, the control device PCS31connected with the station STN31 writes a data “STN31DataL” at anaddress 98 (not depicted) in a low transfer rate block 38 of a sharedmemory area (as a global shared memory area) of the station STN31,whereby the station STN31 works to low-rate transfer the written data“STN31DataL” to a whole of stations STN32 to STN3 n in the network N3with the data transfer system DT8 inclusive.

And, the data transfer system DT8 detects a first transfer timing or athird transfer timing, whereby it works to receive the transferredshared data “STN31DataL”, and store the received shared data“STN31DataL” at an address 98 in a low transfer rate block 38 of ashared memory area (as a global shared memory area 84 a) thereof.

Next, the data transfer system DT8 works to have the shared data“STN31DataL”, as it is stored at the address 98 in the low transfer rateblock 38 of the shared memory area (as the global shared memory area 84a), stored at an address 98 in a low transfer rate block 38 of theshared memory area (as the global shared memory area 82 a). Further, thedata transfer system DT8 works to have the shared data “STN31DataL”, asit is stored at the address 98 in the shared memory area (as the globalshared memory area 82 a), stored at an address 98 in a low transfer rateblock 38 of the shared memory area (as the global shared memory area 80a).

The data transfer system DT8 detects a fourth transfer timing, wherebyit works to low-rate transfer the shared data “STN31DataL” as stored atthe address 98 in the low transfer rate block 38 of the shared memoryarea (as the global shared memory area 82 a) to whole stations STN21 toSTN2 n (FIG. 15 simply depicts the station STN21) connected to thenetwork N2. And, the stations STN21 to STN2 n each respectively have thetransferred shared data “STN31DataL” stored at an address 98 (notdepicted) in a low transfer rate block 38 of a shared memory area (as aglobal shared memory area) thereof.

Further, the data transfer system DT8 detects a second transfer timing,whereby it works to transfer the shared data “STN31DataL” as stored atthe address 98 in the low transfer rate block 38 of the shared memoryarea (as the global shared memory area 80 a) to whole stations STN11 toSTN1 n (FIG. 15 simply depicts the station STN11) connected to thenetwork N1. And, the stations STN11 to STN1 n each respectively have thetransferred shared data “STN31DataL” stored at an address 98 (notdepicted) in a low transfer rate block 38 of a shared memory area (as aglobal shared memory area) thereof.

It therefore is possible for a control device PCS11 to read the data“STN31DataL” transferred to the station STN11 in the network N1, and fora control device PCS21 to read the data “STN31DataL” transferred to thestation STN21 in the network N2.

Such being the case, according to the fifth embodiment, the networkcontrol system 1 e is adapted in addition to effects of the networkcontrol system 1 d according to the fourth embodiment, to have aplurality of transfer rates set for transfer of shared data amongnetworks, allowing for the more enhanced efficiency in use of thenetworks.

Sixth Embodiment

FIG. 16 is a configuration diagram illustrating a system configurationof a network control system 1 f according to a sixth embodiment.

As illustrated in FIG. 16, the network control system 1 f according tothe sixth embodiment includes a data transfer system DT9, and a datatransfer system DT10, in addition to a configuration of network controlsystem 1 according to the first embodiment.

The data transfer system DT9 is connected to stations STN11 to STN1 nthrough a network N4, the data transfer system DT9 and the data transfersystem DT10 being connected to stations STN21 to STN2 n through anetwork N5, the data transfer system DT10 being connected to stationsSTN31 to STN3 n through a network N6.

As illustrated in FIG. 16, the network control system 1 f according tothe sixth embodiment is rendered redundant with networks N1 to N3constituting an A line, and the networks N4 to N6 constituting a B line,to provide wholly duplex network transfer routes. It is likewiserendered redundant with data transfer systems DT1 and DT2 for servicesin the A line, and the data transfer systems DT9 and DT10 for servicesin the B line.

The data transfer system DT1 is always put into a service for datatransfer in the A line, as well as the data transfer system DT9 at aservice in the B line. Also, the data transfer system DT2 is always putinto a service for data transfer in the A line, as well as the datatransfer system DT10 at a service in the B line. It is a station at areception end that determines which line to select for use of data.

That is, at a reception end of the network N1, there is one of stationsSTN11 to STN1 n selecting a normal data out of received data for use. Asbeing given normal data from both lines, it employs data from the Aline. Likewise, at a reception end of the network N2, there is one ofstations STN21 to STN2 n selecting a normal data out of received datafor use. As being given normal data from both lines, it employs datafrom the A line. Further, at a reception end of the network N3, there isone of stations STN31 to STN3 n selecting a normal data out of receiveddata for use. As being given normal data from both lines, it employsdata from the A line.

Such being the case, according to the sixth embodiment, the networkcontrol system 1 f allows for an enhanced availability factor due toduplication, besides a system configuration with cost-reducingsimplification, an enhanced network transfer efficiency, and afacilitated engineering.

Seventh Embodiment

FIG. 17 is a configuration diagram illustrating a system configurationof a network control system 1 g according to a seventh embodiment.

As illustrated in FIG. 17, the network control system 1 g according tothe seventh embodiment includes a data transfer system DT11 in additionto a configuration of network control system 1 d according to the fourthembodiment,

The data transfer system DT11 is connected to stations STN11 to STN1 nthrough a network N4, the data transfer system DT11 being connected tostations STN21 to STN2 n through a network N5, the data transfer systemDT11 being connected to stations STN31 to STN3 n through a network N6.

As illustrated in FIG. 17, the network control system 1 g according tothe seventh embodiment is rendered redundant with networks N1 to N3constituting an A line, and the networks N4 to N6 constituting a B line,to provide wholly duplex network transfer routes. It is likewiserendered redundant with a data transfer system DT7 for services in the Aline, and the data transfer system DT11 for services in the B line.

The data transfer system DT7 is always put into a service for datatransfer in the A line, as well as the data transfer system DT11 at aservice in the B line. It is a station at a reception end thatdetermines which line to select for use of data.

That is, at a reception end of the network N1, there is one of stationsSTN11 to STN1 n selecting a normal data out of received data for use. Asbeing given normal data from both lines, it employs data from the Aline. Likewise, at a reception end of the network N2, there is one ofstations STN21 to STN2 n selecting a normal data out of received datafor use. As being given normal data from both lines, it employs datafrom the A line. Further, at a reception end of the network N3, there isone of stations STN31 to STN3 n selecting a normal data out of receiveddata for use. As being given normal data from both lines, it employsdata from the A line.

Such being the case, according to the seventh embodiment, the networkcontrol system 1 g allows for an enhanced availability factor due toduplication, besides a system configuration with cost-reducingsimplification, an enhanced network transfer efficiency, and afacilitated engineering.

1. A network control system configured for data transfer of shared databetween a first control device and a second control device, the networkcontrol system comprising: a first station configured for control ofdata transfer to a first control device adapted to control equipment asa target thereunder; a second station configured for control of datatransfer to a second control device adapted to control equipment as atarget thereunder; and a data transfer system connected to the firststation through a first network and connected to the second stationthrough a second network, wherein the first station has a first memoryelement configured for storage of a first shared data as one of theshared data, the second station has a second memory element configuredfor storage of a second shared data as one of the shared data, and thedata transfer system comprises: a third memory element configured forstorage of a third shared data as one of the shared data; a fourthmemory element configured for storage of a fourth shared data as one ofthe shared data; a first transfer period determiner configured todetermine a first transfer period as a transfer period for transfer ofthe third shared data from the data transfer system to the firststation; a second transfer period determiner configured to determine asecond transfer period as a transfer period for transfer of the fourthshared data from the data transfer system to the second station; a firsttransfer element configured to operate in accordance with the firsttransfer period, to have the second shared data as stored in the secondmemory element, stored as the fourth shared data in the fourth memoryelement with an address identical to an address thereof in the secondmemory element, and operate in accordance with the second transferperiod, to have the first shared data as stored in the first memoryelement, stored as the third shared data in the third memory elementwith an address identical to an address thereof in the first memoryelement; a second transfer element configured to operate as the thirdshared data is stored by the first transfer element, to have this thirdshared data stored as the fourth shared data in the fourth memoryelement with an address identical to an address thereof in the thirdmemory element, and operate as the fourth shared data is stored by thefirst transfer element, to have this fourth shared data stored as thethird shared data in the third memory element with an address identicalto an address thereof in the fourth memory element; and a third transferelement configured to operate in accordance with the second transferperiod, to have the fourth shared data as stored in the fourth memoryelement, stored as the second shared data in the second memory elementwith an address identical to an address thereof in the fourth memoryelement, and operate in accordance with the first transfer period, tohave the third shared data as stored in the third memory element, storedas the first shared data in the first memory element with an addressidentical to an address thereof in the third memory element.
 2. Thenetwork control system according to claim 1, wherein the data transfersystem further comprises a sixth memory element configured to storetherein sets of addresses of the shared data in the first memoryelement, the second memory element, the third memory element, or thefourth memory element and pieces of information on attributes of beingshared data in association therewith, as share setting information, andis adapted to have the shared data stored in the first memory element,the second memory element, the third memory element, or the fourthmemory element in accordance with the share setting information storedin the sixth memory element.
 3. The network control system according toclaim 1, further comprising a second data transfer system connected tothe first station through the first network and connected to the secondstation through the second network, having an identical configuration tothe data transfer system.
 4. The network control system according toclaim 2, further comprising a second data transfer system connected tothe first station through the first network and connected to the secondstation through the second network, having an identical configuration tothe data transfer system.
 5. A network control system configured fordata transfer of shared data between a first control device and a secondcontrol device, the network control system comprising: a first stationconfigured for control of data transfer to a first control deviceadapted to control equipment as a target thereunder; a second stationconfigured for control of data transfer to a second control deviceadapted to control equipment as a target thereunder; and a data transfersystem connected to the first station through a first network andconnected to the second station through a second network, wherein thefirst station has a first memory element configured for storage of afirst shared data as one of the shared data for each of orders ofpriority in transfer thereof between the data transfer system and thefirst station, the second station has a second memory element configuredfor storage of a second shared data as one of the shared data for eachof orders of priority in transfer thereof between the data transfersystem and the second station, and the data transfer system comprises: athird memory element configured for storage of a third shared data asone of the shared data for each of orders of priority in transferthereof between the data transfer system and the first station; a fourthmemory element configured for storage of a fourth shared data as one ofthe shared data for each of orders of priority in transfer thereofbetween the data transfer system and the second station; a fifth memoryelement configured to store therein sets of orders of priority intransfer of the shared data between the data transfer system and thefirst station and between the data transfer system and the secondstation, as priority order information; <a first transfer perioddeterminer configured to read a piece of the priority order informationfrom the fifth memory element, and operate on a basis of this priorityorder information to determine a first transfer period as a transferperiod for transfer of the third shared data from the data transfersystem to the first station; a second transfer period determinerconfigured to read a piece of the priority order information from thefifth memory element, and operate on a basis of this priority orderinformation to determine a second transfer period as a transfer periodfor transfer of the fourth shared data from the data transfer system tothe second station; a first transfer element configured to operate inaccordance with the first transfer period, to have the second shareddata as stored in the second memory element, stored as the fourth shareddata in the fourth memory element with an address identical to anaddress thereof in the second memory element, and operate in accordancewith the second transfer period, to have the first shared data as storedin the first memory element, stored as the third shared data in thethird memory element with an address identical to an address thereof inthe first memory element; a second transfer element configured tooperate as the third shared data is stored by the first transferelement, to have this third shared data stored as the fourth shared datain the fourth memory element with an address identical to an addressthereof in the third memory element, and operate as the fourth shareddata is stored by the first transfer element, to have this fourth shareddata stored as the third shared data in the third memory element with anaddress identical to an address thereof in the fourth memory element;and a third transfer element configured to operate in accordance withthe second transfer period, to have the fourth shared data as stored inthe fourth memory element, stored as the second shared data in thesecond memory element with an address identical to an address thereof inthe fourth memory element, and operate in accordance with the firsttransfer period, to have the third shared data as stored in the thirdmemory element, stored as the first shared data in the first memoryelement with an address identical to an address thereof in the thirdmemory element.
 6. The network control system according to claim 5,wherein the data transfer system further comprises a sixth memoryelement configured to store therein sets of addresses of the shared datain the first memory element, the second memory element, the third memoryelement, or the fourth memory element and pieces of information onattributes of being shared data in association therewith, as sharesetting information, and is adapted to have the shared data stored inthe first memory element, the second memory element, the third memoryelement, or the fourth memory element in accordance with the sharesetting information stored in the sixth memory element
 7. The networkcontrol system according to claim 5, further comprising a second datatransfer system connected to the first station through the first networkand connected to the second station through the second network, havingan identical configuration to the data transfer system.
 8. The networkcontrol system according to claim 6, further comprising a second datatransfer system connected to the first station through the first networkand connected to the second station through the second network, havingan identical configuration to the data transfer system.
 9. A networkcontrol system comprising control devices adapted to control equipmentsas targets thereunder, stations configured for control of data transferto the control devices, and a data transfer system connected to thestations through networks, the network control system being configuredfor data transfer of shared data shared to be common among the controldevices, wherein the stations have seventh memory elements thereofconfigured for storage of a seventh shared data as one of the shareddata, and the data transfer system comprises: an eighth memory elementconfigured for storage of an eighth shared data as one of the shareddata in shared memory areas thereof corresponding to the stationsrespectively; a transfer period determiner configured to determinetransfer periods for the stations, one each for transfer of the eighthshared data from the data transfer system to one of the stations; afirst transfer element configured to operate in accordance with acorresponding transfer period out of the transfer periods with respectto any one station out of the stations, to have the seventh shared dataas stored in one of the seventh memory elements at another station thansaid one station, stored as the eighth shared data in one of the sharedmemory areas of the eighth memory element corresponding to the otherstation, second transfer element configured to operate as the eighthshared data is stored in a shared memory area out of the shared memoryareas of the eighth memory element by the first transfer element, tohave this eighth shared data stored, with an address identical to anaddress thereof in the shared memory area, in another shared memory areaout of the shared memory areas of the eighth memory element; and a thirdtransfer element configured to operate in accordance with saidcorresponding transfer period, to have the eighth shared data as storedin a certain one of the shared memory areas of the eighth memoryelement, stored as the seventh shared data in one of the seventh memoryelements at said one station, with an address identical to an addressthereof in the certain shared memory area of the eighth memory element.10. The network control system according to claim 9, wherein the datatransfer system further comprises a tenth memory element configured tostore therein sets of addresses of the shared data in the seventh memoryelement or the eighth memory element and pieces of information onattributes of being shared data in association therewith, as sharesetting information, and is adapted to have the shared data stored inthe seventh memory element or the eighth memory element in accordancewith the share setting information stored in the tenth memory element.11. The network control system according to claim 9, further comprisinga second data transfer system connected to the stations throughnetworks, having an identical configuration to the data transfer system.12. The network control system according to claim 10, further comprisinga second data transfer system connected to the stations throughnetworks, having an identical configuration to the data transfer system.13. A network control system comprising control devices adapted tocontrol equipments as targets thereunder, stations configured forcontrol of data transfer to the control devices, and a data transfersystem connected to the stations through networks, the network controlsystem being configured for data transfer of shared data shared to becommon among the control devices, wherein the stations have seventhmemory elements thereof configured for storage of a seventh shared dataas one of the shared data for each of orders of priority in transferthereof between the data transfer system and the stations, and the datatransfer system comprises: an eighth memory element configured forstorage of an eighth shared data as one of the shared data in sharedmemory areas thereof corresponding to the stations respectively, foreach of orders of priority in transfer thereof between the data transfersystem and the stations; a ninth memory element configured to storetherein sets of orders of priority in transfer of the shared databetween the data transfer system and the stations, as priority orderinformation; a transfer period determiner configured to read pieces ofthe priority order information from the ninth memory element, andoperate on a basis of this priority order information to determinetransfer periods for the stations, one each for transfer of the eighthshared data from the data transfer system to one of the stations; afirst transfer element configured to operate in accordance with acorresponding transfer period out of the transfer periods with respectto any one station out of the stations, to have the seventh shared dataas stored in one of the seventh memory elements at another station thansaid one station, stored as the eighth shared data in one of the sharedmemory areas of the eighth memory element corresponding to the otherstation, a second transfer element configured to operate as the eighthshared data is stored in a shared memory area out of the shared memoryareas of the eighth memory element by the first transfer element, tohave this eighth shared data stored, with an address identical to anaddress thereof in the shared memory area, in another shared memory areaout of the shared memory areas of the eighth memory element; and a thirdtransfer element configured to operate in accordance with saidcorresponding transfer period, to have the eighth shared data as storedin a certain one of the shared memory areas of the eighth memoryelement, stored as the seventh shared data in one of the seventh memoryelements at said one station, with an address identical to an addressthereof in the certain shared memory area of the eighth memory element.14. The network control system according to claim 13, wherein the datatransfer system further comprises a tenth memory element configured tostore therein sets of addresses of the shared data in the seventh memoryelement or the eighth memory element and pieces of information onattributes of being shared data in association therewith, as sharesetting information, and is adapted to have the shared data stored inthe seventh memory element or the eighth memory element in accordancewith the share setting information stored in the tenth memory element.15. The network control system according to claim 13, further comprisinga second data transfer system connected to the stations throughnetworks, having an identical configuration to the data transfer system.16. The network control system according to claim 14, further comprisinga second data transfer system connected to the stations throughnetworks, having an identical configuration to the data transfer system.